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chapter 17 notes and infotop Isotopes , Atomic Numbers and Mass Numbers How big are electrons? Atomic Structure MORE ON THE Atom THE SHELL MODEL & PERIODIC TABLE The Modern View of Atomic Structure bottom ATOMSATOMS consist of a nucleus containing PROTONS and NEUTRONS and a cloud of ELECTRONS orbiting around it. ATOMS are the smallest particle that have unique characteristics and properties, i.e. ELEMENTS There are 90 NATURALLY OCCURRING ELEMENTS (ORGANIC) and A neutral atom will have the same number of PROTONS(+) & ELECTRONS(-) All atoms with the same number of PROTONS ( their ATOMIC NUMBER) can only be one element When a neutral atom ELECTRONS are lost the NET CHARGE becomes POSITIVE The number of electrons equals the number of protons when an atom is NEUTRALLY CHARGED, if it is not neutral in charge it is then an ION If the number of NEUTRONS doe not match the number of PROTONS the atom is the an ISOTOPE of that ELEMENT Most ATOMS have an equal number of PROTONS and NEUTRONS, when the # of NEUTRONS is different they are then ISOPTOPES of the ELEMENT ATOMS consist of a nucleus containing PROTONS and NEUTRONS and a cloud of ELECTRONS orbiting around it. 90% of the mass of the universe is Hydrogen Stars are made up of primarily Hydrogen ORGANIC ELEMENTS Almost all of the heavy elements (heavier than Hydrogen) were formed deep inside huge stars probably a long time ago A neutral atom will have the same number of PROTONS(+) & ELECTRONS(-)
The ATOMIC NUMBER on the PERIODIC TABLE defines a unique ELEMENT by its number of PROTONS Most ATOMS have an equal number of PROTONS and NEUTRONS When the NUMBER of NEUTRONS is different than the NUMBER of PROTONS it is then called an ISOTOPE of that ELEMENT MOst ATOMS have and EQUAL NUMBER of ELECTRONS and PROTONS addition or subtraction of add or subtract PROTONS -> DIFFERENT ELEMENT ATOMS appx. 10-10 m, Dia 0.000 000 000 000 1 PROTONS & NEUTRONS appx. 10-15 m dia. 0.000 000 000 000 001 100,000 times smaller than the atom ELECTRONS appx. 10-10 m dia 0.000 000 000 000 000 001 m ATOM is 100,000 times larger in dameter than the NUCLEONS and 100,000,000 times bigger than an electron
Isotopes, Atomic Numbers and Mass Numbers How big are electrons? Atomic Structure MORE ON THE Atom THE SHELL MODEL & PERIODIC TABLE THE SHELL MODEL & PERIODIC TABLEWHERE DID THEY COME FROM? WHEN? ALMOST ALL of the 90 NATURALLY OCCURRING or ORGANIC ELEMENTS in the universe were created deep in the interior of GIANT STARS during SUPERNOVAS where those stars collapsed upon themselves and then exploded only extremely large stars produce the kinds of temperatures and pressures needed to fuse atoms of lighter elements such as Hydrogen(H) or Helium(He) into heavier elements like metals Sodium (Na) or Iron (Fe) MOST HEAVY ELEMENTS ARE MUCH OLDER THAN OUR SOLAR SYSTEM NUCLEUS IS EXTREMELY SMALL compared to the ATOM ITSELF ELECTRONS and the SHELL MODEL The SHELL MODEL of the ATOM describes the electrons as orbiting in 7 UNIQUE SHELLS The SHELLS represent discrete ORBITS or ENERGY LEVELS that are filled from the INNERMOST SHELL outward The f. ELECTRONS orbit the NUCLEUS in what are described as SHELLS (also know as Quantum, or ENERGY LEVELS) One model of the ATOM describes the ELECTRONS as orbiting the nucleus in discrete SHELLS, (also called ORBITS or LEVELS (QUANTUM) The SHELLS are populated by a MAXIMUM number of 2 ELECTRONS in the INNERMOST SHELL and as many as 32 in the 7th OUTERMOST SHELL The shells are filled with ELECTRONS from as few as 1 in the INNERMOST SHELL to as many as 32 in the outermost shells Each ROW on the PERIODIC TABLE represents ONE SHELL PERIODIC TABLE & CH-CH-CH-CHANGES - WHEN YOU CHANGE THINGSAdd or subtract PROTONS and YOU HAVE A DIFFERENT ELEMENT DIFFERENT # of NEUTRONS are still the same element but a called an ISOTOPE 51 # of NEUTRONS WILL VARY for the same element, Changing the number of PROTON changes an atom to a different ELEMENT PROTONS and NEUTRONS are both NUCLEONS and
differ only in charge NEUTRONS have a NEUTRAL (i.e. no charge) The NUCLEUS contains almost all of the MASS of an ATOM but occupies on a FEW QUADRILLIONTHS of the total VOLUME ELECTRONS are also extremely small in volume and also in mass. A NEUTRON or PR has more mass than over 2,000 ELECTRONS PROTONS and NEUTRONS differ only in charge and are made up of identical particles called QUARKS The ATOMIC NUMBER on the PERIODIC TABLE defines a unique ELEMENT by its number of PROTONS When the NUMBER of NEUTRONS is different than the NUMBER of PROTONS it is still the same element but is called an ISOTOPE of that ELEMENT TWO HYDROGEN ISOTOPES
ONLY ONE ELEMENT can have THAT NUMBER OF PROTONS and ANY ATOM with THAT NUMBER OF PROTONS IS THAT ELEMENT example: An ATOM with 6 PROTONS can only be the element CARBON and has ATOMIC NUMBER 6 REMOVE 1 PROTON from CARBON and you end up with an ELEMENT with ATOMIC NUMBER 5, that element can only be BORON ADD 1 PROTON to CARBON and you end up with an ELEMENT with ATOMIC NUMBER 7, that element can only be NITROGEN To find out what element it would change into find the original element on the periodic table, MOVE LEFT FOR EACH PROTON REMOVED or MOVE RIGHT FOR EACH PROTON ADDED to find out what the new ELEMENT would be, when at the beginning of a row go to the end of the previous row when subtracting or the beginning of the next row when adding SOURCES http://web.jjay.cuny.edu/~acarpi/NSC/3-atoms.htm Atomic Structure, Anthony Carpi Since all atoms are composed of protons, electrons and neutrons, all chemical and physical differences between elements are due to the differences in the number of these sub-atomic particles. Therefore, an atom is the smallest sample of an element, because dividing an atom further (into sub-atomic particles) destroys the element's unique identitity. Isotopes, Atomic Numbers and Mass NumbersWhat characteristic feature of sub-atomic particles distinguishes one element from another?
top Isotopes , Atomic Numbers and Mass Numbers How big are electrons? Atomic Structure MORE ON THE Atom THE SHELL MODEL & PERIODIC TABLE The Modern View of Atomic Structure bottom How big are electrons?Even with the most high powered microscope, we still can’t SEE electrons, so how do we know they exist? Electrons are too small to see, but we can WEIGH them.The mass of one electron = 9.10 x 10-28 grams In order to obtain a gram of electrons, we would need approximately:1 000 000 000 000 000 000 000 000 000 electrons Therefore, 2.7 billion billion billion (2.7 x1027) electrons would weigh the same as a penny! Although we cannot see electrons, we can see that they have been excited and involved in reactions due to colour changes or the production of light. An electron is a negatively charged subatomic particle. They are responsible for the formation of chemical compounds. Electrons are considered to be fundamental units of matter (they are not made up of smaller units). Although scientists have been studying electrons for quite a while, the exact diameter of an electron is unknown. According to Malcolm H. Mac Gregor,
The electron was the first subatomic particle to be discovered. It was discovered in 1897 by a British physicist named Sir Joseph John Thomson. Later, in 1913, an American Physicist by the name of Robert A. Millikan obtained an accurate measurement of the electron's charge. Recent studies show that the charge of an electron is 1.60218 x 10-19 coulombs. The mass of an electron is known to be 9.10939 x 10-31 kilograms. In all neutral atoms there are the same number of electrons as protons. Electrons are bound to the nucleus by electrostatic forces. Most of the volume of an atom is occupied by electrons, even though they barley contribute to the atomic mass. Neils Bohr, Wolfgang Pauli, and others discovered the pattern in which electrons are distributed throughout an atom in the 1920s. Electrons are arranged at various distances from the nucleus, and are arranged in energy levels called shells. The average distance of outer electrons from the nucleus is a few tens of nanometers in all atoms. In heavy atoms inner electrons are much closer to the nucleus. The number of electrons in outermost shell determines the chemical behavior of that atom. If an atom combines with another atom to form a molecule, than the electrons in the outermost shell are transferred from one atom to another or shared between atoms. "The diameter of an electron is less than 1/1000 the diameter of a proton. A proton has a diameter of approximately 1/25,000,000,000,000 inch (0.000000000001 mm)."
top Isotopes , Atomic Numbers and Mass Numbers How big are electrons? Atomic Structure MORE ON THE Atom THE SHELL MODEL & PERIODIC TABLE The Modern View of Atomic Structure bottom MORE ON THE AtomAtoms are made of smaller particles, called electrons, protons, and neutrons. An atom consists of a cloud of electrons surrounding a small, dense nucleus of protons and neutrons. Electrons and protons have a property called electric charge, which affects the way they interact with each other and with other electrically charged particles. Electrons carry a negative electric charge, while protons have a positive electric charge. The negative charge is the opposite of the positive charge, and, like the opposite poles of a magnet, these opposite electric charges attract one another. Conversely, like charges (negative and negative, or positive and positive) repel one another. The attraction between an atom’s electrons and its protons holds the atom together. Normally, an atom is electrically neutral, which means that the negative charge of its electrons is exactly equaled by the positive charge of its protons. The nucleus contains nearly all of the mass of the atom, but it occupies only a tiny fraction of the space inside the atom. The diameter of a typical nucleus is only about 1 × 10-14 m (4 × 10-13 in), or about 1/100,000 of the diameter of the entire atom. The electron cloud makes up the rest of the atom’s overall size. If an atom were magnified until it was as large as a football stadium, the nucleus would be about the size of a grape. Electrons are tiny, negatively charged particles that form a cloud around the nucleus of an atom. Each electron carries a single fundamental unit of negative electric charge, or –1. The electron is one of the lightest particles with a known mass. A droplet of water weighs about a billion, billion, billion times more than an electron. Physicists believe that electrons are one of the fundamental particles of physics, which means they cannot be split into anything smaller. Physicists also believe that electrons do not have any real size, but are instead true points in space—that is, an electron has a radius of zero. Electrons act differently than everyday objects because electrons can behave as both particles and waves. Actually, all objects have this property, but the wavelike behavior of larger objects, such as sand, marbles, or even people, is too small to measure. In very small particles wave behavior is measurable and important. Electrons travel around the nucleus of an atom, but because they behave like waves, they do not follow a specific path like a planet orbiting the Sun does. Instead they form regions of negative electric charge around the nucleus. These regions are called orbitals, and they correspond to the space in which the electron is most likely to be found. As we will discuss later, orbitals have different sizes and shapes, depending on the energy of the electrons occupying them. Protons carry a positive charge of +1, exactly the opposite electric charge as electrons. The number of protons in the nucleus determines the total quantity of positive charge in the atom. In an electrically neutral atom, the number of the protons and the number of electrons are equal, so that the positive and negative charges balance out to zero. The proton is very small, but it is fairly massive compared to the other particles that make up matter. A proton’s mass is about 1,840 times the mass of an electron. Neutrons are about the same size as protons but their mass is slightly greater. Without neutrons present, the repulsion among the positively charged protons would cause the nucleus to fly apart. Consider the element helium, which has two protons in its nucleus. If the nucleus did not contain neutrons as well, it would be unstable because of the electrical repulsion between the protons. (The process by which neutrons hold the nucleus together is explained below in the Strong Force section of this article.) A helium nucleus needs either one or two neutrons to be stable. Most atoms are stable and exist for a long period of time, but some atoms are unstable and spontaneously break apart and change, or decay, into other atoms. Unlike electrons, which are fundamental particles, protons and neutrons are made up of other, smaller particles called quarks. Physicists know of six different quarks. Neutrons and protons are made up of up quarks and down quarks—two of the six different kinds of quarks. The fanciful names of quarks have nothing to do with their properties; the names are simply labels to distinguish one quark from another. Quarks are unique among all elementary particles in that they have electric charge top Isotopes , Atomic Numbers and Mass Numbers How big are electrons? Atomic Structure MORE ON THE Atom THE SHELL MODEL & PERIODIC TABLE The Modern View of Atomic Structure The Modern View of Atomic Structure http://wine1.sb.fsu.edu/chm1045/notes/Atoms/AtomStr2/Atoms03.htm Physicists have identified a long list of particles which make up the atomic nucleus. Chemists, however, are primarily concerned with the following sub-atomic particles:
Note: a convenient unit of measurement for atomic distances is the angstrom (Å). The angstrom is equal to 1 x 10-10 meters. Thus, top Isotopes , Atomic Numbers and Mass Numbers How big are electrons? Atomic Structure MORE ON THE Atom THE SHELL MODEL & PERIODIC TABLE
Atomic StructureAn updated version of this lesson is available at Visionlearning: Atomic Theory & Ions & Isotopes An atom cannot be broken down further without changing the chemical nature
of the substance. For example, if you have 1 ton, 1 gram or 1 atom of oxygen,
all of these units have the same properties. We can break down the atom of
oxygen into smaller particles, however, when we do the atom looses its chemical
properties. For example, if you have 100 watches, or one watch, they all behave
like watches and tell time. You can dismantle one of the watches: take the back
off, take the batteries out, peer inside and pull things out. However, now the
watch no longer behaves like a watch. So what does an atom look like inside?
top Isotopes , Atomic Numbers and Mass Numbers How big are electrons? Atomic Structure MORE ON THE Atom THE SHELL MODEL & PERIODIC TABLE The Modern View of Atomic Structure bottom |
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IF
THIS WAS A NEUTRON AN ELECRON WOULD BE 
,
protons 
and neutrons 
.
These particles have different properties. Electrons are tiny, very
light particles that have a negative electrical charge (-).
Protons are much larger
and heavier than electrons and have the opposite charge, protons have a positive
charge. Neutrons
are large and heavy like protons, however neutrons have no electrical charge.
Each atom is made up of a combination of these particles. Let's look at one
type of atom: 
