The Atom & Subatomic Particles

What we knew by 1932:What we knew by 1932:

1.0087 amu1.0087 amu

(or 1 amu)(or 1 amu)

00neutron neutron 11nn

1.0073 amu1.0073 amu

(or 1 amu)(or 1 amu)

+1+1proton proton 11p or p or 11HH

0.0005486 amu0.0005486 amu

(or 0 amu)(or 0 amu)

-1-1electron electron 00ee

Relative MassRelative MassRelative ChargeRelative Charge

--11

11 11

00

Location of Subatomic ParticlesLocation of Subatomic Particles

• electrons located electrons located outside nucleusoutside nucleus

• protons & neutrons located protons & neutrons located inside nucleusinside nucleus

Atomic NumberAtomic Number

atomic number:atomic number: = size of nuclear charge= size of nuclear charge

= number of protons in nucleus= number of protons in nucleus determines identity of elementdetermines identity of element gives order to PTgives order to PT

For neutral atoms:For neutral atoms:atomic number = # protons = # electronsatomic number = # protons = # electrons

Mass NumberMass Number

= =

# protons + # neutrons# protons + # neutrons

IsotopesIsotopes

atoms of same element can have different atoms of same element can have different mass numbersmass numbers

# protons must be the same so …# protons must be the same so …

# neutrons must be different# neutrons must be different

Dalton’s theory must be modified:Dalton’s theory must be modified:

the atom is divisiblethe atom is divisible

presence of subatomic particlespresence of subatomic particles

atoms of same element can be differentatoms of same element can be different

isotopes have different # neutronsisotopes have different # neutrons

NotationNotation

1212CC66

•left left superscriptsuperscript is is mass numbermass number

•left left subscriptsubscript is is atomic numberatomic number

NotationNotation

1212CC66

12 = # protons + neutrons12 = # protons + neutrons 6 = # protons6 = # protons

12 – 6 = 6 neutrons12 – 6 = 6 neutrons

How many neutrons in this How many neutrons in this atom?atom?

1717OO88

Mass number is ?Mass number is ?

Atomic number is ?Atomic number is ?

# of neutrons is ?# of neutrons is ?

# of electrons in atom is?# of electrons in atom is?

1717

88

17 – 8 17 – 8

88

= 9= 9

Mass number is ?Mass number is ?

Atomic number is ?Atomic number is ?

# of neutrons is ?# of neutrons is ?

# of electrons in atom is?# of electrons in atom is?

1515

NN77

1515

77

15 – 715 – 7

77

= 8= 8

Mass number is ?Mass number is ?

Atomic number is ?Atomic number is ?

# of neutrons is ?# of neutrons is ?

# of electrons in atom is?# of electrons in atom is?

FF 1919

99

19 – 9 = 1019 – 9 = 10

99

19

Other NotationsOther Notations

C-C-1212

# after symbol is # after symbol is mass numbermass number!!

must look up atomic numbermust look up atomic number

What’s the difference between What’s the difference between H-1, H-2, and H-3?H-1, H-2, and H-3?

All H’s have 1 protonAll H’s have 1 proton

1 proton, so it must have ? neutrons1 proton, so it must have ? neutrons

H-1: mass # = 1H-1: mass # = 1

1 proton, ? neutrons1 proton, ? neutrons

H-2: mass # = 2H-2: mass # = 2

1 proton, so it must have ? 1 proton, so it must have ? neutronsneutronsH-3: mass # = 3H-3: mass # = 3

00

11

22

Consider U-234, U-235, & U-238Consider U-234, U-235, & U-238

What’s the atomic number of U?What’s the atomic number of U? How many protons in U?How many protons in U? How many neutrons in U-234?How many neutrons in U-234? How many neutrons in U-235?How many neutrons in U-235? How many neutrons in U-238?How many neutrons in U-238? How many electrons in U?How many electrons in U?

9292

9292234 – 92 = 142234 – 92 = 142

235 – 92 = 143235 – 92 = 143

238 – 92 = 146238 – 92 = 146

9292

How many neutrons in Po-217?How many neutrons in Po-217?

What’s the atomic number?What’s the atomic number?

How many protons?How many protons?

So the neutrons are …So the neutrons are …

8484

8484

217 – 84 = 133 neutrons!217 – 84 = 133 neutrons!

IONSIONS

IONS = atoms that gained or lost IONS = atoms that gained or lost electronselectrons

protons and electrons aren't = anymore, so protons and electrons aren't = anymore, so ions are ions are not not neutral they carry a charge (+/-)neutral they carry a charge (+/-)

IONSIONS

Charge of ion: Charge of ion:

= # protons minus # electrons = # protons minus # electrons

(subtract the electrons since are negative)(subtract the electrons since are negative)

IONSIONS

If atom loses electrons, it has more (+) If atom loses electrons, it has more (+) protons than (-) electronsprotons than (-) electrons What kind of ion is it?What kind of ion is it?

If atom gains electrons, it has more (-) If atom gains electrons, it has more (-) electrons than (+) protonselectrons than (+) protons What kind of ion is it?What kind of ion is it?

positivepositive

negativenegative

Charge of IonsCharge of Ions

Ion chargeIon charge: : right superscriptright superscriptClCl-1-1 a chloride ion with a charge of -1a chloride ion with a charge of -1

NaNa+1+1 a sodium ion with a charge of +1a sodium ion with a charge of +1

OO-2-2 an oxygen ion with a charge of -2an oxygen ion with a charge of -2

If no right superscript, it’s understood to be zero and If no right superscript, it’s understood to be zero and therefore a neutral atomtherefore a neutral atom

Putting it all togetherPutting it all together

How many protons, neutrons, & electrons How many protons, neutrons, & electrons in each of the followingin each of the following

2323NaNa+1+1

11

2525MgMg+2+2

1212

3434SS-2-2

1616

6464ZnZn+2+2

3030

1919FF-1-1

99

1313NN-3-3

77

11 p, 12 n, 10 e11 p, 12 n, 10 e

12 p, 13 n, 10 e12 p, 13 n, 10 e

16 p, 18 n, 18 e16 p, 18 n, 18 e 9 p, 10 n, 10 9 p, 10 n, 10 ee

30 p, 34 n, 28 e30 p, 34 n, 28 e 7 p, 6 n, 10 7 p, 6 n, 10 ee

Lost Lost 1 e1 e--

Got Got 2 e-2 e-

Got Got 1 e-1 e-

Lost Lost 2 e-2 e-

Lost Lost 2 e-2 e-

Got Got 3 e-3 e-

What is an amu?What is an amu?

atomic mass unitatomic mass unit

amu amu 1/12 the mass of the C-12 atom 1/12 the mass of the C-12 atom