Atoms and the Periodic Table. Atoms Atoms are the smallest pieces of matter that contain all the...

Atoms and the Atoms and the Periodic TablePeriodic Table

AtomsAtoms

Atoms are the smallest Atoms are the smallest pieces of matter that pieces of matter that contain all the properties contain all the properties of a specific elementof a specific element

Each element contains Each element contains only one type of atomonly one type of atom

Atomic ModelsAtomic Models

Have been revised many times to Have been revised many times to explain new discoveriesexplain new discoveries

Democritus (4Democritus (4thth century B.C.) century B.C.) thought all matter was made of thought all matter was made of particles he called the atomparticles he called the atom

Theory was modified when Theory was modified when subatomic particles were discoveredsubatomic particles were discovered

Atomic ModelsAtomic Models

Plum Pudding Model Plum Pudding Model (1904) developed (1904) developed by J.J. Thomsonby J.J. Thomson

Planetary Model Planetary Model (1911) developed by (1911) developed by Ernest Rutherford Ernest Rutherford

Newer ModelsNewer Models

Bohr’s Model (1913)Bohr’s Model (1913) Developed by Developed by Niels BohrNiels Bohr

Electron Cloud Electron Cloud Model (1925) Model (1925)

Inside the AtomInside the Atom

Atoms are made up of smaller particlesAtoms are made up of smaller particles These particles are found in different These particles are found in different

regions of the atomregions of the atom

Protons (pProtons (p++))

Positively charged particles found Positively charged particles found in nucleus of atomin nucleus of atom

Have an electrical charge of +1Have an electrical charge of +1 Mass of 1 a.m.u.Mass of 1 a.m.u. Composed of quarksComposed of quarks Discovered by Ernest Rutherford Discovered by Ernest Rutherford

using Gold Foil Experiment using Gold Foil Experiment

ProtonsProtons The number of protons in an atom The number of protons in an atom

determines its identity determines its identity

All oxygen atoms have 8 protons, all All oxygen atoms have 8 protons, all uranium atoms have 92 protonsuranium atoms have 92 protons

If the number of protons change the If the number of protons change the identity of the atom changes.identity of the atom changes.

Neutrons (nNeutrons (n00))

Neutral particles found in nucleus Neutral particles found in nucleus of atomof atom

Have no electrical chargeHave no electrical charge Mass of 1 a.m.u.Mass of 1 a.m.u. Composed of quarksComposed of quarks Discovered by James ChadwickDiscovered by James Chadwick

NucleusNucleus

The nucleus is the positively charged The nucleus is the positively charged dense core in the center of the atomdense core in the center of the atom

Houses protons and neutronsHouses protons and neutrons Contains 99.9% of mass of atomContains 99.9% of mass of atom Extremely small compared to the Extremely small compared to the

entire size of the atom entire size of the atom

Electrons (eElectrons (e--))

Negatively charged particles found in Negatively charged particles found in electron cloudelectron cloud

Have an electrical charge of -1Have an electrical charge of -1 Constantly moving around outside Constantly moving around outside

nucleusnucleus Have essentially no massHave essentially no mass Discovered by J.J. Thomson during Discovered by J.J. Thomson during

cathode ray experimentcathode ray experiment

ElectronsElectrons

The number of electrons in a neutral The number of electrons in a neutral atom is equal to the number of atom is equal to the number of protonsprotons

Neutral oxygen has 8 protons, Neutral oxygen has 8 protons, therefore it has 8 electronstherefore it has 8 electrons

Neutral lead has 82 protons, therefore, Neutral lead has 82 protons, therefore, it has 82 electronsit has 82 electrons

Valence ElectronsValence Electrons

Electrons in the outermost energy Electrons in the outermost energy level of an atom are called valence level of an atom are called valence electronselectrons

These are the electrons furthest from These are the electrons furthest from the nucleusthe nucleus

SymbolsSymbols

Elements are identified by their Elements are identified by their chemical symbolschemical symbols

Symbols are usually either one capital Symbols are usually either one capital letter like C for Carbon, or one capital letter like C for Carbon, or one capital and one lowercase letter like Ne for and one lowercase letter like Ne for NeonNeon

Atomic Number (Z)Atomic Number (Z)

Whole number shown on periodic tableWhole number shown on periodic table Periodic table is arranged by atomic Periodic table is arranged by atomic

numbernumber

Atomic Number = # of Atomic Number = # of ProtonsProtons

*Also gives the number of *Also gives the number of electrons if the atom is neutral electrons if the atom is neutral

Atomic NumberAtomic Number

Mass Number (A)Mass Number (A)

The mass number is the sum of the The mass number is the sum of the total number of protons and neutrons total number of protons and neutrons in the atomin the atom

Mass # = # pMass # = # p++ + # n + # n00

Atom MathAtom Math

Atomic Number

Symbol

Element Name

Atomic Mass

IsotopesIsotopes

Isotopes are atoms of the same element Isotopes are atoms of the same element that have different numbers of neutronsthat have different numbers of neutrons

All atoms are isotopesAll atoms are isotopes

Each element has isotopes that are more Each element has isotopes that are more common than otherscommon than others

Nuclear SymbolNuclear Symbol

Isotopes can be designated with their Isotopes can be designated with their nuclear symbolnuclear symbol

Hyphen NotationHyphen Notation

Isotopes can also be designated using Isotopes can also be designated using hyphen notationhyphen notation

Carbon-16Carbon-16

Element Name Mass Number

Write the Nuclear Symbol and Hyphen Write the Nuclear Symbol and Hyphen Notation for the Following IsotopesNotation for the Following Isotopes

Lithium isotope with 3 protons and 4 Lithium isotope with 3 protons and 4 neutronsneutrons

Sulfur isotope with 17 neutronsSulfur isotope with 17 neutrons

Lead with 122 neutronsLead with 122 neutrons

IonsIons

Ions are atoms or groups of atoms Ions are atoms or groups of atoms that have a net positive or negative that have a net positive or negative chargecharge

The charge results from an unequal The charge results from an unequal number of electrons and protons number of electrons and protons within atom of group of atomswithin atom of group of atoms

Ions Ions

Ions with more electrons than protons Ions with more electrons than protons have a negative chargehave a negative charge For each extra electron the negative For each extra electron the negative

charge increases by onecharge increases by one

Ions with less electrons than protons Ions with less electrons than protons have a positive chargehave a positive charge For each missing electron the positive For each missing electron the positive

charge increases by onecharge increases by one

Ions Ions

The charge of an ion is indicated on The charge of an ion is indicated on its element symbol with a positive or its element symbol with a positive or negative sign on the upper right side negative sign on the upper right side and number equal to the magnitude of and number equal to the magnitude of the chargethe charge

The number one is not included The number one is not included

Ions Ions

FF-- 9 protons – 10 electrons = -1 9 protons – 10 electrons = -1 chargecharge

CaCa2+2+ 20 protons – 18 electrons = -2 20 protons – 18 electrons = -2 chargecharge

PP3-3- 15 protons – 18 electrons = -3 15 protons – 18 electrons = -3 chargecharge

Common Ions (Need to Common Ions (Need to memorize these) memorize these)

Many of the main group elements in the Many of the main group elements in the same column form ions with same chargesame column form ions with same charge

Column 1 (Li, Na, K, Rb, Cs): +1Column 1 (Li, Na, K, Rb, Cs): +1 Column 2 (Be, Mg, Ca, Sr, Ba): +2Column 2 (Be, Mg, Ca, Sr, Ba): +2 Column 13 (Al, Ga): +3Column 13 (Al, Ga): +3 Column 15 (N, P, As): -3Column 15 (N, P, As): -3 Column 16 (O, S, Se, Te): -2Column 16 (O, S, Se, Te): -2 Column 17 (F, Cl, Br, I): -1Column 17 (F, Cl, Br, I): -1

Atomic MassAtomic Mass

The average atomic mass is The average atomic mass is the number at the bottom of the number at the bottom of this squarethis square

Found by averaging the Found by averaging the natural abundances of natural abundances of its isotopes its isotopes

Calculating Average Calculating Average Atomic Mass (amu)Atomic Mass (amu)

If abundance is given as percent If abundance is given as percent value:value:

If abundance is given as decimal If abundance is given as decimal value:value:

100

abundance) Isotope)(% of (Mass Mass Atomic

bundance)Isotope)(a of (Mass Mass Atomic

Average Atomic Mass Average Atomic Mass

Rubidium has two common isotopes, Rb-85 and Rb-87. If the abundance of 85Rb is 72.2% and the abundance of 87Rb is 27.8%, what is the average atomic mass of rubidium?

amu 865.85100

)]8.27)(87[()]2.72)(85[(

Uranium has three common isotopes. If the abundance of 234U is 0.0001, the abundance of 235U is 0.0071, and the abundance of 238U is .9928, what is the average atomic mass of uranium?

amu 23897.238)]9928.238()0071.235()0001.234[(

Electron ConfigurationElectron Configuration

An electron configuration is a shorthand An electron configuration is a shorthand description of how electrons are arranged description of how electrons are arranged around the nucleus of an atom. around the nucleus of an atom.

Electrons generally do not orbit the nucleus Electrons generally do not orbit the nucleus rather, they move in certain patterns based rather, they move in certain patterns based on on three factorsthree factors: (1) their energies, (2) their : (1) their energies, (2) their orientations in space and (3) their angular orientations in space and (3) their angular momentum momentum

A. General RulesA. General Rules

Pauli Exclusion PrinciplePauli Exclusion Principle

Each orbital can hold TWO electrons with Each orbital can hold TWO electrons with

opposite spins.opposite spins.


Aufbau PrincipleAufbau Principle

Electrons fill the Electrons fill the lowest energy lowest energy orbitals first.orbitals first.

““Lazy Tenant Lazy Tenant Rule”Rule”

O

8e-

Orbital DiagramOrbital Diagram

Electron ConfigurationElectron Configuration

1s2 2s2 2p4

B. NotationB. Notation

1s 2s 2p

RIGHTWRONG


Hund’s RuleHund’s Rule Within a sublevel, place one eWithin a sublevel, place one e-- per orbital per orbital

before pairing them.before pairing them.

““Empty Bus Seat Rule”Empty Bus Seat Rule”

Shorthand ConfigurationShorthand Configuration

S 16e-

Valence Electrons

Core Electrons

S 16e- [Ne] 3s2 3p4

1s2 2s2 2p6 3s2 3p4

B. NotationB. Notation

Longhand ConfigurationLonghand Configuration


Period #Period # energy level (subtract for d & f)energy level (subtract for d & f)

A/B Group # A/B Group # total # of valence etotal # of valence e--

Column within sublevel blockColumn within sublevel block # of e# of e-- in sublevel in sublevel

s-block

1st Period

1s11st column of s-block


Example - Example - HydrogenHydrogen

1

2

3

4

5

6

7


Shorthand ConfigurationShorthand Configuration Core eCore e--:: Go up one row and over to the Go up one row and over to the

Noble Gas.Noble Gas. Valence eValence e--:: On the next row, fill in the # of On the next row, fill in the # of

ee-- in each sublevel. in each sublevel.

[Ar] 4s2 3d10 4p2


Example - Example - GermaniumGermanium

Full energy levelFull energy level

1

2

3

4 5

6

7

Full sublevel (s, p, d, f)Full sublevel (s, p, d, f) Half-full sublevelHalf-full sublevel

D. StabilityD. Stability

Electron Configuration ExceptionsElectron Configuration Exceptions CopperCopper

EXPECTEXPECT:: [Ar] 4s[Ar] 4s22 3d 3d99

ACTUALLYACTUALLY:: [Ar] 4s[Ar] 4s11 3d 3d1010

Copper gains Copper gains stabilitystability with a full with a full d-sublevel.d-sublevel.


Electron Configuration ExceptionsElectron Configuration Exceptions ChromiumChromium

EXPECTEXPECT:: [Ar] 4s[Ar] 4s22 3d 3d44

ACTUALLYACTUALLY:: [Ar] 4s[Ar] 4s11 3d 3d55

Chromium gains Chromium gains stabilitystability with a half-full d- with a half-full d-sublevel.sublevel.



Ion FormationIon Formation Atoms gain or lose electrons to become more Atoms gain or lose electrons to become more

stable.stable. Isoelectronic with the Noble Gases.Isoelectronic with the Noble Gases.

OO2- 2- 10e10e- - [He] 2s[He] 2s22 2p 2p66


Ion Electron ConfigurationIon Electron Configuration Write the eWrite the e-- config for the closest Noble Gas config for the closest Noble Gas

EXEX: Oxygen ion : Oxygen ion O O2-2- Ne Ne

D. Lewis DiagramsD. Lewis Diagrams

Also called Also called electron dot diagramselectron dot diagrams Dots represent the valence eDots represent the valence e--

ExEx: Sodium: Sodium ExEx: Chlorine: Chlorine

Lewis Diagram for Oxygen

Steps to Draw Lewis Steps to Draw Lewis StructuresStructures

1.1. Determine how many valence are in the element.Determine how many valence are in the element.

2.2. Staring on the Right side of the element draw a Staring on the Right side of the element draw a dot to represent a valence electron.dot to represent a valence electron.

3.3. Place one dot on each side of the symbol. One Place one dot on each side of the symbol. One electron must be drawn around each side of the electron must be drawn around each side of the element before a second electron can be added element before a second electron can be added to any side.to any side.

Steps to Draw Lewis Steps to Draw Lewis StructuresStructures

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