Atoms

Smallest part of all matterMade of smaller particles

DaltonRutherfordThompson Chadwick

Bohr

Protons•Positively charged•Found in the nucleus•Identifies element•Gives the element its atomic number•Gives nucleus its positive charge•Contributes to the atom’s reactivity• +

NEUTRONSNeutrally charged-no chargeFound in the nucleusContributes to the mass of the atom ‘n’

ELECTRONSoNegatively chargedoFound on the energy shellsoDetermines the reactivity of the atomoHas very small mass-not normally considered when calculating mass of atom.o e

Elements can be classified as

Metals: found on the left side of the periodic table less than 4 valence electrons

solids at room temperature

Nonmetals: found on the right side of the periodic table

more than 4 valence electronsgases at room temperature

Noble gases: found in the last column unreactive under normal situations gases at room temperature

Nucleus: protons and neutrons

+= n=

K shell: holds2 electrons

L shell: holds 8 electrons

M shell: holds 8 electrons(can hold up to 18 electrons)

Lithium

• Bohr model

Atomic mass = 7Atomic number = 3

= 3

n = 4

e = 3

++

n 4

3

Electron configuration: 2-1

Electron dot diagram is a way of representingonly the outer most shell. This shell is calledthe valence shell, is often unstable, and will be the shell involved in bonding.

Li F

What can we tell about an atom if we know atomicNumber and mass?

Atomic mass 14 atomic number 7

= 7 electron configuration = 2-5

n = 7 e dot = N

e = 7

Element is a nonmetal

+

+ = 7n=7

Elements can be classified as

Metals: found on the left side of the periodic table less than 4 valence electrons

solids at room temperature

Nonmetals: found on the right side of the periodic table

more than 4 valence electronsgases at room temperature

Noble gases: found in the last column unreactive under normal situations gases at room temperature

Periodic table arranges elements according to

atomic numberatomic number increases by one as

we read from left to right atomic number will determine

reactivity

H

Li

Na

K

Be

Mg

Ca

B

Al

C

Si

N

P

O

S

F

Cl

He

Ne

Ar

1

2

3

4

I

II III IV V VI VII

VIII O

Remember, valence means having to do withthe last shell.

Atoms like to use the least amount of energy.that means, they like to have their electronspaired and to have the valence shell stable with 8 electrons.

There are only 6 elements that naturally existin this stable state. They are …….

Noble gases

Atoms that are not stable cause trouble –they can be flammable, explosive, toxic.These problems are what make an atomreactive – meaning they want to becomestable. Bonding:

Ionic loss or gain of electronsCovalent sharing of electrons

IONIC BONDING: OCCURS BETWEEN-

METALS: LESS THAN 4 VALENCE ELECTRONSAND

NONMETALS: MORE THAN 4 VALENCE ELECTRONS

***REMEMBER: ATOMS WANT TO USE LITTLE E!!

METALS WILL LOSE ELECTRONSNONMETALS WILL GAIN THOSE ELECTRONS LOST

Ionic Bonding: occurs between metal and nonmetal

> 4 val. e < 4 val. E

lose e gain eform ions – charged atoms because

the # of protons does NOTequal # electrons.

+ ion - ion

Na: metal, > 4 val. e, lose e

F: nonmetal, < 4 val. e, gain e

NaF sodium flouride

+

-

Li2O

+

+

2-

Bonding between atoms is a result of:a. atoms need to be stableb. atoms need to exist in a lower

energy statec. attraction of positive nucleus and

negative electronsd. size of the atom’s radius

Atomic radius=distance betweennucleus and valence shell.the + nucleus will hold the – electronson the atom by means of attractiveforces. As atomic radius gets larger, attractive forces get smaller – electronslost easily. That’s good for a metal.as atomic radius gets smaller, attractiveforces get stronger. That’s good for anonmetal.

H

Li

Na

K

Be

Mg

Ca

B

Al

C

Si

N

P

O

S

F

Cl

He

Ne

Ar

1

2

3

4

I

II III IV V VI VII

VIII O

COVALENT BONDINGSHARING OF ELECTRONSATOMS REMAIN NEUTRAL

OCCURS BETWEEN:2 NONMETALS

A NONMETAL AND A METALLOIDHYDROGEN AND ALL NONMETALS

PRODUCES WEAK BONDSPRODUCES COMPOUNDS THAT HAVE LOW

MELTING POINTSALL ORGANIC COMPOUNDS ARE COVALENT

COVALENT BONDSBetween hydrogen and A nonmetal

Fluorine has 7 valence electronsIt needs 8 in order to exist in a lowerEnergy state. It could bond ionically With A metal or covalently with hydrogenby sharing one of its valence electrons.

Hydrogen has only one Electron and therefore will neverLose that electron. In order forIt to become stable and existIn a lower energy state, it willShare its only electron withfluorine

COVALENT BONDINGBETWEEN2 NONMETALS

Nonmetals, because they have more than 4 valence electrons and especially those that have small atomic radii, will bond with them-selves in order to become stable and exist at a lower energy state.

These atoms will be called DIATOMS. There are 7 diatomsThat you will need to memorize. They are F, Cl, Br, I, O, N, H.

COVALENT BONDINGBETWEEN

NONMETAL AND A METALLOIDCarbon will be our only metalloid with 4 valence electrons

Fluorine is a Nonmetal with 7 Valence electrons

The resulting stable cmpdContains 4 F and 1 C. Because the atoms never LOST E’s they remainneutral.

Comparison of bonds

• Ionic Bonding: • occurs between metal

and nonmetal• lose e gain e• form ions – charged

atoms

• COVALENT BONDING SHARING OF ELECTRONS

ATOMS REMAIN NEUTRAL

OCCURS BETWEEN: 2 NONMETALS

A NONMETAL AND A METALLOID

HYDROGEN AND ALL NONMETALS

POLARITYUNEVEN DISTRIBUTION OF CHARGES

__ +

On polar molecules, electrons are controlled by oneOf the atoms.