ATOMIC ATOMIC NUMBERNUMBER

The atomic number of an element is The atomic number of an element is the number of protons in the nucleus the number of protons in the nucleus of that element. of that element.

The atomic number determines the The atomic number determines the identity of the atom. identity of the atom.

  

Location of Location of

Subatomic ParticlesSubatomic Particles

Protons and Neutrons lie in the NucleusProtons and Neutrons lie in the Nucleus

Electron lie outside the nucleusElectron lie outside the nucleus

P & N

E

nucleus

E = electronP = ProtonN = Neutron

Atoms of the same element can have Atoms of the same element can have different masses. different masses.

They have the same number of protons They have the same number of protons and electrons but different numbers of and electrons but different numbers of neutrons.neutrons.

These atoms are called These atoms are called isotopesisotopes of the of the element.element.

EAZ

ISOTOPIC NOTATION

Mass Number (Sum of Protons and Neutrons in Nucleus)

Atomic Number (Number of Protons in Nucleus)

Symbol of Element

Examples of IsotopesExamples of Isotopes

ElementElement ProtonsProtons ElectronsElectrons NeutronsNeutrons SymbolSymbolHydrogenHydrogen 1 1 11 00 11

11HH

HydrogenHydrogen 1 1 11 11 1122H H

HydrogenHydrogen 1 1 11 22 1133HH

UraniumUranium 92929292 143 143 9292235235UU

UraniumUranium 92929292 146 146 9292238238UU

ChlorineChlorine 17 171717 1818 1717

3535ClCl

ChlorineChlorine 17 171717 2020 17173737ClCl

BOHR MODEL OF THE ATOMBOHR MODEL OF THE ATOM Niels Bohr knew that light was absorbed and emitted Niels Bohr knew that light was absorbed and emitted

by atoms. by atoms.

He used ideas and principles from Quantum He used ideas and principles from Quantum Mechanics to suggest a model of the hydrogen atom.Mechanics to suggest a model of the hydrogen atom.

  

The orbits of an electron in atom are quantized which The orbits of an electron in atom are quantized which means that each orbit corresponds to a fixed means that each orbit corresponds to a fixed energy.Electrons that travel in these orbits are stable energy.Electrons that travel in these orbits are stable and do not emit light.and do not emit light.

Light is emitted or absorbed when an electron jumps Light is emitted or absorbed when an electron jumps from one orbit to another.from one orbit to another.

Electron Orbitals

The orbits were later called shells and then even later The orbits were later called shells and then even later energy levels.energy levels.

  

Electrons tend to fill the energy levels closest to the Electrons tend to fill the energy levels closest to the nucleus first.nucleus first.

   The maximum number of electron in any energy The maximum number of electron in any energy

level is given by 2nlevel is given by 2n22

  

When an electron jumps from the lowest energy level to a When an electron jumps from the lowest energy level to a higher level, light is absorbed by the atom.higher level, light is absorbed by the atom.

   When an electron jumps from a higher energy level to a When an electron jumps from a higher energy level to a

lower energy light is emitted by the atom.lower energy light is emitted by the atom.

Bohr's model explained the emission spectrum of hydrogen.Bohr's model explained the emission spectrum of hydrogen.

ShellShell SubshellSubshell Energy LevelEnergy Level Max # of Max # of ElectronsElectrons

KK s s 1 1 2 2 (1s(1s22))

LL s, p s, p 2 2 8 8 (2s(2s22 2p 2p66))

MM s,p,d s,p,d 3 3 18 18 (3s(3s22 3p 3p66 3d 3d1010))

NN s,p,d,f s,p,d,f 4 4 32 32 (4s(4s22 4p 4p66 4d 4d1010

4f4f1414)) Think of the shells as the floors in an apartment building. Think of the subshells as the different apartments on each floor. For example on the 1st Floor, all you have is apartment 1s. On the 2nd Floor you have apartment 2s and 2p. On the 3rd Floor you have apartment 3s, 3p and 3d. On the 4th Floor you have apartment 4s, 4p and 4d and 4f. Apartment s can hold 2 people (electrons), Apartment p can hold six people (electrons), Apartment d can Hold 10 people (electrons) andApartment f can hold 14 people (electrons)

max =2max = 8

max = 8max = 8

Simplified Electron Configuration (CHM02)

Ca4020

(1s(1s22 2s 2s22 2p 2p66 3s 3s22 3p 3p66 4s 4s22 3d 3d00))

Electron Structures Using the Bohr ModelElectron Structures Using the Bohr Model ElementElement ElectronElectron Group Group Period Period

StructureStructure

11HH 11 (1s(1s11)) I I 1 1

22HeHe 22 (1s(1s22)) II II 1 1

33LiLi 2-12-1 (1s(1s2 2 2s 2s11)) I I 2 2

44BeBe 2-22-2 (1s(1s2 2 2s 2s22)) II II 2 2

55BB 2-32-3 (1s(1s2 2 2s 2s2 2 2p 2p11)) III III 2 2

66CC 2-42-4 (1s(1s2 2 2s 2s2 2 2p 2p22)) IV IV 2 2

77NN 2-52-5 (1s(1s2 2 2s 2s2 2 2p 2p33)) V V 2 2

88OO 2-62-6 (1s(1s2 2 2s 2s2 2 2p 2p44)) VI VI 2 2

99FF 2-72-7 (1s(1s2 2 2s 2s2 2 2p 2p55)) VII VII 2 2

1010NeNe 2-82-8 (1s(1s2 2 2s 2s2 2 2p 2p66)) VIII VIII 2 2

1818ArAr 2-8-82-8-8 (1s(1s2 2 2s 2s2 2 2p 2p66 3s 3s22 3p 3p66)) VIII VIII 3 3

2020CaCa 2-8-8-22-8-8-2 (1s(1s2 2 2s 2s2 2 2p 2p66 3s 3s22 3p 3p66 4s 4s22)) II II 4 4

LEWIS STRUCTURES OF ATOMSLEWIS STRUCTURES OF ATOMS Valence electrons are the outermost electrons of Valence electrons are the outermost electrons of

an atom.an atom.

Na with the electron structure 2-8-1, has 1 Na with the electron structure 2-8-1, has 1 valence electron.valence electron.

Fluorine with the electron structure 2-7 has 7 Fluorine with the electron structure 2-7 has 7 valence electronsvalence electrons

In a Lewis Structure of an atom, dots are used to In a Lewis Structure of an atom, dots are used to show the valence electrons of atoms.show the valence electrons of atoms.

A capital letter represents the nucleus of the atoms aA capital letter represents the nucleus of the atoms a

When writing Lewis structures, imagine each When writing Lewis structures, imagine each symbol to be enclosed in a square.symbol to be enclosed in a square.

The electron dot structures are obtained by adding The electron dot structures are obtained by adding the first two electrons to one corner. Add the the first two electrons to one corner. Add the remaining electrons to a side until all of the valence remaining electrons to a side until all of the valence electrons are shownelectrons are shown

F

F

F F F FF F

Aluminum has 3 valence electrons:Aluminum has 3 valence electrons:

Oxygen has 6 valence electronsOxygen has 6 valence electrons

Al

O

Lewis Octet RuleLewis Octet Rule All atoms with the exception of hydrogen tend to All atoms with the exception of hydrogen tend to

form bonds until they have 8 electrons in the outer form bonds until they have 8 electrons in the outer shell.shell.

All atoms have zero charge because they contain All atoms have zero charge because they contain equal numbers of protons and electronsequal numbers of protons and electrons

Sodium (Na)Sodium (Na)11 electrons11 electrons ++ 11 protons11 protons11(-1)11(-1) ++ 11(+1)11(+1) == 00

Calcium (Ca)Calcium (Ca)20 electrons20 electrons ++ 20 protons20 protons20(-1)20(-1) ++ 20(+1)20(+1) == 00

Formation of IonsFormation of Ions An ion is a charged particle.An ion is a charged particle.

It is formed by either adding or removing electrons It is formed by either adding or removing electrons from an atom.from an atom.

Adding electrons to an atom results in the formation Adding electrons to an atom results in the formation of negative ions (i.e., of negative ions (i.e., anionanion).).

Removal of electrons from an atom results in the Removal of electrons from an atom results in the formation of a positive ion (i.e., formation of a positive ion (i.e., cationcation).).

Formation of AnionsFormation of Anions

Cl + eCl + e-- Cl Cl--

O + 2eO + 2e-- O O2-2-

N + 3eN + 3e-- N N3-3-

Formation of CationsFormation of Cations

Na Na Na Na+ + ++ ee--

Ca Ca Ca Ca2+ 2+ ++ 2e2e--

Li Li Li Li+ + ++ ee--

The Ionic BondThe Ionic Bond An ionic bond results from the attraction An ionic bond results from the attraction

between positive and negative ions. between positive and negative ions.

Positive and negative ions result from electron Positive and negative ions result from electron transfer.transfer.

Sodium atom Na

Chlorine atom Cl

11+11e-

1 e-

17+ 17e- 11+ 17+

10e-18e-

Na+Sodium ion

Cl-Chloride ion

Periodic Table Location and Ionic ChargePeriodic Table Location and Ionic Charge

The charge on an ion can be predicted from the The charge on an ion can be predicted from the position of an element in the periodic table for position of an element in the periodic table for AA family elements.family elements.

GroupGroup IAIA IIAIIA IIIAIIIA IVAIVA VAVA VIAVIA VIIAVIIA VIIIAVIIIA

Charge +1Charge +1 +2+2 +3 +3 -3 -3 -2 -2 -1 0 -1 0