The AtomThe Atom

The AtomThe Atom

The atom has The atom has three parts:three parts:

1)1) ProtonsProtons

2)2) NeutronsNeutrons

3)3) ElectronsElectrons

ProtonsProtons Protons:Protons:

1)1) Found in the nucleusFound in the nucleus

2)2) Mass: one (1) Atomic Mass UnitMass: one (1) Atomic Mass Unit

3)3) have a (+) positive charge, have a (+) positive charge,

11 PPROTON = 1 ROTON = 1 PPOSITIVEOSITIVE ChargeCharge

Protons (Cont’d)Protons (Cont’d) On the periodic table, each element is On the periodic table, each element is

numbered. This number equals the numbered. This number equals the number of number of ProtonsProtons in the nucleus. in the nucleus.

NeutronsNeutrons

Also found in the nucleus.Also found in the nucleus. Mass: one (1) Atomic Mass Unit.Mass: one (1) Atomic Mass Unit. They have They have NONO charge. charge. NeutrNeutron on = =

NeutrNeutralal

ElectronsElectrons Found around the nucleus (like planets around the Found around the nucleus (like planets around the

Sun)Sun) An An ElectronElectron’s mass is almost nothing…almost’s mass is almost nothing…almost Have a negative (-) chargeHave a negative (-) charge

EELLEECTRONS = NCTRONS = NEEGATIVGATIVEE

Standard Atomic NotationStandard Atomic Notation

Be

9

4

Mass Number = mass of all the protons and neutrons in the nucleus

Atomic Number = number of protons in the nucleus and the number of electrons orbiting the nucleus

Element Symbol – eg. Beryllium

To find the number of neutrons in the nucleus, subtract atomic number from mass number. There would be 9 – 4 or 5 neutrons in a Beryllium atom

RememberRemember

The periodic table is organized by The periodic table is organized by atomic number (the number of atomic number (the number of protons the element has in its protons the element has in its nucleus)nucleus)

Protons are + and electrons are - Protons are + and electrons are - The number of protons = the number The number of protons = the number

of electrons (positives = negatives)of electrons (positives = negatives)

Let’s try some!Let’s try some!

Have your periodic table readyHave your periodic table ready How many protons, neutrons and How many protons, neutrons and

electrons in one atom of:electrons in one atom of: Hydrogen?Hydrogen? Carbon?Carbon? Beryllium?Beryllium? Calcium?Calcium? Fluorine?Fluorine?

1 p+, 1 e-, 0 n

20 p+, 20 e-, 20 n

6 p+, 6 e-, 6 n4 p+, 4 e-, 5 n

9 p+, 9 e-, 10 n

Bohr-Rutherford DiagramsBohr-Rutherford Diagrams

Named after the Named after the work done by Neils work done by Neils Bohr and Ernest Bohr and Ernest Rutherford (nobody Rutherford (nobody before them gets any before them gets any respect!)respect!)

Flattened model of Flattened model of the inside of an atomthe inside of an atom

Unique for each atomUnique for each atom

Electron ShellsElectron Shells

Nucleus12 P12 N

1 2

First Shell, maximum 2 electrons

2 elements in first row (period)

Why only 2 in the first shell?Why only 2 in the first shell?

Electron ShellsElectron Shells

Nucleus12 P12 N

1 2

3 4

5

6

7

8

9

10

Second Shell,Maximum 8 electrons

Why 8 in the second shell?Why 8 in the second shell?

8 elements in second period

Electron ShellsElectron Shells

Nucleus12 P12 N

1 2

3 4

5

6

7

8

9

10

11 12

Third shell, max # 8 electrons

Note: Magnesium only needs 2 electrons in this shell because it has 12 total

Bohr-Rutherford DiagramsBohr-Rutherford Diagrams

Nucleus12 P12 N

1 2

3 4

5

6

7

8

9

10

11 12

Eg. Magnesium

Guess this elementGuess this element

82 protons = element 82 which is LEAD82 protons = element 82 which is LEAD

The Noble GasesThe Noble Gases

Column to the far right of the periodic Column to the far right of the periodic table, He, Ne, Ar, Kr, Xe, & Rntable, He, Ne, Ar, Kr, Xe, & Rn

Nucleus2 P2 N

1 2

Nucleus10 P10 N

1 2

3 4

5

6

7

8

9

10

So, how would Magnesium look like So, how would Magnesium look like Neon?Neon?

Nucleus12 P12 N

1 2

3 4

5

6

7

8

9

10

11 12

Magnesium Neon

Nucleus10 P10 N

1 2

3 4

5

6

7

8

9

10

So, if Mg lost two So, if Mg lost two Electrons, Electrons, but still had the but still had the same number of same number of ProtonsProtons, what is its , what is its Charge?Charge?

+2+2

Nucleus12 P12 N

1 2

3 4

5

6

7

8

9

10

ChargesCharges

The outer The outer electronselectrons on an atom are on an atom are called: called: ValenceValence electronselectrons. .

Atoms want a Atoms want a Bohr-Rutherford Bohr-Rutherford Diagram Diagram that look like the Noble that look like the Noble Gases because… Gases because… have the most stable structurehave the most stable structure Won’t react when mixedWon’t react when mixed

Usually, this means the atom ends up Usually, this means the atom ends up with a with a Charge.Charge.

FluorineFluorine

What does F need to look like a Noble gas?What does F need to look like a Noble gas? If we add one If we add one Electron,Electron, what will the what will the

Charge Charge of the atom be?of the atom be? - 1- 1

Nucleus9 P9 N

1 2

3 4

5

6

7

8

9

10

IonsIons Ion=Ion= a a Charged Charged atom in which the number atom in which the number

of of ELECTRONS (-)ELECTRONS (-) is different from the is different from the number of number of PROTONS (+)PROTONS (+)..

Ionic Charge= Ionic Charge= is the number of is the number of positive (+) positive (+) or or negative (-) negative (-) Charges Charges on an atom. Ex: Mgon an atom. Ex: Mg+2+2

Nucleus12 P12 N

1 2

3 4

5

6

7

8

9

10

GroupsGroups

Mg

Nucleus12 P12 N

12

3 4

5

6

7

8

9

10

11 12

1 2

3 4

Nucleus4 P4 N

Be (Berylium)

So…So…

Even though each element has a Even though each element has a different # of different # of PROTONS PROTONS and and ELECTRONSELECTRONS, each element in a group , each element in a group has a similar has a similar Bohr-Rutherford DiagramBohr-Rutherford Diagram

This means they want to This means they want to gaingain or or loselose the same number of the same number of Electrons.Electrons.

It also means elements in a Group will It also means elements in a Group will react similarly in Chemical Reactionsreact similarly in Chemical Reactions