Virtually everything that is, is made up of atoms. Chapter 12, page 361 Balloon and sweeter animation

Sub-Particles in the Atom Each element is chemically unique. To understand why they are unique, you need to know the structure of the atom (the smallest particle of an element) and the characteristics of its components. Element = made of one kind of Atom. Li Compounds = made of different atoms chemically bonded in whole number ratios. H 2 O Mixtures are physical combinations of elements or compounds with variable composition O 2 + H 2. Particles or Pure substances

Sub-Particle Mass Charge Location in the Atom proton~1 a.m.u. 1+ in nucleus neutron~1 a.m.u. 0 in nucleus electron~0 a.m.u. 1- orbits nucleus Sub-Particles in the Atom atomic.mass.unit= a.m.u. ~ ×10 −27 kg or 1/12 the mass of C-12kg

Structure of the Atom There are two regions The nucleus With protons and neutrons – Positive charge – Almost all the mass Electron cloud – Most of the volume of an atom – The region where the electron can be found

Size of an atom Atoms are incredibly tiny. Measured in picometers ( meters) – Hydrogen atom, 32 pm radius Nucleus tiny compared to atom – Radius of the nucleus near m. – Density near g/cm 3 IF the atom was the size of a stadium, the nucleus would be the size of a marble. California WEB

Balloon and sweeter animation Balloon and sweeter animation What holds an atom together? Nuclear Tug-Of-War Electrostatic force – like charges repel and un-like charges attract Strong Nuclear Force – holds nucleons (p+ & n0) together, very strong nuclear force but over short distances – Stable nuclei are SMALL – Large nuclei tend to be unstable (radioactive) Electrostatic Force – Holds electrons on atom

Counting Particles in Atoms Atomic Number = number of protons (p+) = unique for each element Atomic Mass Number = Mass of an atom = number of protons + neutrons = (p+) + (no); (e- do not have mass) California WEB 12 6 C 14 6 C 12 6 C Mass Number = A Atomic Number = Z

How can I remember how many protons or electrons there are? Just remember the A.P.E. rules! atomic number = number of protons= number of electrons

Now, how do I remember how many protons there are? Just remember the M.A.N.! mass number - Atomic number= number of neutrons

Neon Ne Protons: Electrons: Neutrons: Atomic Number: 10 Atomic Mass: 20 10

Phosphorus P Protons:15 Electrons: Neutrons: 16 Atomic Number: Atomic Mass: 15 31

Aluminum Al Protons: Electrons: 13 Neutrons: 14 Atomic Number: Atomic Mass: 13 27

Argon Ar Protons:18 Electrons: Neutrons: Atomic Number: Atomic Mass:

Silicon Si Protons: Electrons: Neutrons: 14 Atomic Number: 14 Atomic Mass: 14 28

Symbols Contain the symbol of the element, the mass number and the atomic number (top heavy) X Mass number Atomic number # protons + # neutrons mass number

Symbols Find the – Atomic number – Mass number – number of electrons – number of protons – number of neutrons F 19 9 = 9 = 10 = 9 = 19 +

So let’s practice!

Symbols Find the –number of protons –number of neutrons –number of electrons –Atomic number –Mass number Br = 35 = 45 = 35 = 80

Symbols Find the – number of protons – number of neutrons – number of electrons – Atomic number – Mass number Na Sodium atom = 11 = 12 = 11 = 23

To find net charge on an atom, consider the p + and the e –. cation: a (+) ion -- more p + than e – -- formed when atoms lose e – anion: a (–) ion -- more e – than p + atoms -- formed when gain e – ion: a charged atom e-e- p+p+ n0 n and -4 = e-e- p+p+ n0 n and -2 = +1 Ions

Symbols Find the – number of protons – number of neutrons – number of electrons – Atomic number – Mass number Na Sodium ion = 11 = 12 = 10 = 11 = 23

Symbols If an element has an atomic number of 23 and a mass number of 51 what is the –number of protons –number of neutrons –number of electrons –Complete symbol V = 23 = 28 = 23

Symbols If an element has 60 protons and 84 neutrons what is the –Atomic number –Mass number –number of electrons –Complete symbol Nd = 60 = 144 = 60

Symbols If a neutral atom of an element has 78 electrons and 117 neutrons what is the –Atomic number –Mass number –number of protons –Complete symbol Pt = 78 = 195 = 78

Masses of Atoms  Mass Number  Isotopes  Ions  Relative Atomic Mass  Average Atomic Mass Courtesy Christy Johannesson

Mass Number mass number= protons + neutrons always a whole number NOT on the Periodic Table! Nucleus Electrons Nucleus Neutron Proton Carbon-12 Neutrons 6 Protons 6 Electrons6 e-

Isotopes Atoms of the same element with different mass numbers. Mass # Atomic # Nuclear symbol: carbon-12Hyphen notation: carbon-12 Courtesy Christy Johannesson C

Isotopes Dalton was wrong. Atoms of the same element can have different numbers of neutrons. different mass numbers. called isotopes.

Isotopes Nucleus Electrons Nucleus Neutron Proton Carbon-12 Neutrons 6 Protons 6 Electrons6 Nucleus Electrons Carbon-14 Neutrons 8 Protons 6 Electrons Nucleus Neutron Proton

What is an isotope? same number of protons, different numbers of neutrons. Boron-10BProtons:Electrons:Neutrons: Atomic Number: 5 Atomic Mass:10 Boron-11BProtons:Electrons:Neutrons: Atomic Number: 5 Atomic Mass: B B 5 B B 5

Carbon- C Protons: Electrons: Neutrons: 6 Atomic Number: 6 Atomic Mass: What is the average atomic mass of Carbon? Carbon- C Protons: 6 Electrons: Neutrons: Atomic Number: Atomic Mass:

Isotopes Chlorine-37 – atomic #: – mass #: – # of protons: – # of electrons: – # of neutrons: Courtesy Christy Johannesson Cl Cl

Writing Isotopes Put the mass number after the name of the element carbon- 12 carbon -14 uranium-235 – Or California WEB 12 6 C Mass # Atomic # 12 6 C

Using a periodic table and what you know about atomic number, mass, isotopes, and electrons, fill in the chart: ElementSymbolAtomic Number Mass # # of protons # of neutron # of electron charge 888 Potassium 39+1 Br Atomic Number = Number of Protons Number of Protons + Number of Neutrons = Atomic Mass Atom (no charge) : Protons = Electrons Ion (cation) : Protons > ElectronsIon (anion) : Electrons > Protons

Using a periodic table and what you know about atomic number, mass, isotopes, and electrons, fill in the chart: ElementSymbolAtomic Number Mass # # of protons # of neutron # of electron charge 888 Potassium 39+1 Br Oxygen Bromine Zinc O K Zn Atomic Number = Number of Protons Number of Protons + Number of Neutrons = Atomic Mass Atom (no charge) : Protons = Electrons Ion (cation) : Protons > ElectronsIon (anion) : Electrons > Protons A N S W E R K E Y

Isotopes Because of the existence of isotopes, the mass of a collection of atoms has an average value. Average mass = ATOMIC WEIGHT = ATOMIC MASS Boron is 20% B-10 and 80% B-11. – That is, B-11 is 80 percent abundant on earth. For boron atomic mass = 0.20 (10 amu) (11 amu) = 10.8 amu

Average Atomic Mass massed average of all isotopes on the Periodic Table round to 2 decimal places Courtesy Christy Johannesson Avg. Atomic Mass = (mass)(%) + (mass)(%) 100

Average Atomic Mass EX: Calculate the avg. atomic mass of oxygen if its abundance in nature is 99.76% O-16, 0.04% O-17, and 0.20% O-18. Courtesy Christy Johannesson Avg. Atomic Mass = (16)(99.76) + (17)(0.04) + (18)(0.20) 100 = amu

Average Atomic Mass EX: Find chlorine’s average atomic mass if approximately 8 of every 10 atoms are chlorine-35 and 2 are chlorine-37. Courtesy Christy Johannesson Avg. Atomic Mass = (35)(8) + (37)(2) 10 = amu

Assume you have only two atoms of chlorine. One atom has a mass of 35 amu (Cl-35) The other atom has a mass of 36 amu (Cl-36) What is the average mass of these two isotopes? 35.5 amu Looking at the average atomic mass printed on the periodic table...approximately what percentage is Cl-35 and Cl-36? 55% Cl-35 and 45% Cl-36 is a good approximation Cl