Atomic Composition

Unit 3 – Nuclear Model of the atom

What do we know about atoms?

The atom is made of subatomic particles called nucleons.There are different types of nucleons

ELECTRON e-

Negatively Charged

Atomic Mass – 0.0005 amu

Basically round to zero amu

3 Major Subatomic Particles

PROTON p+

Positive Charge

Mass of 1.007 amu

Found in nucleus of atom

Neutron no

No charge - “neutral”

Mass of 1.0009 amu

Found in Nucleus

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Symbol -ZAll atoms of

the same element have

the same number of protons in

the nucleus.

Atomic Number

ATOMIC NUMBER = NUMBER OF PROTONS

Symbol -AMass comes from the nucleus of the atom.

Mass number = # protons + # neutrons

Mass Number

No overall Charge

Number of protons and electrons are

the sameNumber of neutrons =

mass number minus atomic

number

Neutral Atom -0r- Ground State

Nitrogen?protons, neutrons, electrons

Copper?protons, neutrons, electrons

PROTONS = 29

NEUTRONS= 35

ELECTRONS= 29

PROTONS = 7

NEUTRONS= 7

ELECTRONS= 7

Ion

There was either:

1. Gain of electron(s)

2. Loss of electron(s)

What if it is not neutral?

X+

X-

Calculating nucleons in an ion Example: How

many protons, neutrons and electrons are there in Mg +2

In an atom or ion the number of protons is always the same. (atomic number)

If an atom is not electrically neutral than

there is an imbalance of the proton to

electron ratio and we have an ion.

If we have an ion one of two scenarios are

present:Protons are in greater number than electrons so we have a positive

ion. Protons are in less

number than electrons so we have a negative

ion.

Mg +2

?proton neutrons electrons

Calculating the number of neutrons is the Mass number minus the atomic number

Calculating electrons in an ion we have to look at the charge on the ion. If the ion is positive then there are more protons than electrons and if the number is negative then there are more electrons than protons

In an atom or ion the

number of protons is always the

same. (atomic number)

Mg +2

?proton neutrons electrons

Magnesium has a mass number of 24 so the NEUTRONS =

24 (mass #) – 12(atomic #) = 12

Magnesium has a charge of a +2 so the number of protons are 2 more than the number of electrons. Since the number of protons does not change we will subtract 2 from the atomic number to give us ELECTRONS=

12 (atomic #) -2(the number on the charge = 10 the number of electrons.

Magnesium has an

atomic number of 12 so the

PROTONS = 12

Al+3

?proton neutrons electronsO-2

?proton neutrons electrons

PROTON = 8

NEUTRON = 16-8=8

ELECTRON = 8+2=10

PROTON = 13

NEUTRON = 27-13=14

ELECTRON = 13-3=10

Metals vs. NonmetalsMETALS LOSE ELECTRONS BECOMING POSITIVELY CHARGED.

NONMETALS GAIN ELECTRONS BECOMING NEGATIVELY CHARGED.

How do we write all of this information?

Complete Chemical Symbol

Write the symbol for the atom with 28 protons, 28 electrons and 31 neutrons.

Ni1. Look up the symbol by using the number of protons. REMEMBER: the number of protons is the same as the atomic number.

2. Write the number of protons in the lower left hand side of the element.

28

3. Add the # of neutrons to the number of protons. REMEMBER - this is the atomic mass.

59

4. Check to see if you have an atom or an ion. If the number or protons does not equal the number of electrons then you will need to add a + charge or a – charge.

How do we write all of this information?

Complete Chemical Symbol

Write the symbol for the ion with 8 protons, 10 electrons and 8 neutrons.

O1. Look up the symbol by using the number of protons. REMEMBER: the number of protons is the same as the atomic number.

2. Write the number of protons in the lower left hand side of the element.

8

3. Add the # of neutrons to the number of protons. REMEMBER - this is the atomic mass.

16

4. Check to see if you have an atom or an ion. If the number or protons does not equal the number of electrons then you will need to add a + charge or a – charge.

-2

How do we write all of this information?

Complete Chemical Symbol

Write the symbol for the ion with 20 protons, 18 electrons and 20 neutrons.

Ca 1. Look up the

symbol by using the number of protons. REMEMBER: the number of protons is the same as the atomic number.

2. Write the number of protons in the lower left hand side of the element.

20

3. Add the # of neutrons to the number of protons. REMEMBER - this is the atomic mass.

40

4. Check to see if you have an atom or an ion. If the number or protons does not equal the number of electrons then you will need to add a + charge or a – charge.

+2

How do we write all of this information?

Element name – atomic mass

How many protons, neutrons and electrons are in Tantalum-181.

1. The number of protons comes from the atomic number.

2. The number of electrons equals the number protons because this is a neutral atom.

Protons – 73 Electrons – 73 Neutrons – 108

3. The number of neutrons is equal to the mass number minus the atomic number.

Now it your turn to practiceComplete the in class practice WS

Example Using the Bohr Model

Na is a metal and wants to lose an electron so it has a full energy level of electrons.

Cl is a nonmetal and wants to gain and electron so it can have a full energy level.

1s22s22p6

3s1

1s22s22p63s2

3p5

Example Using the Bohr Model

11 protons and 10 electrons make an ion with a +1 charge.

17 protons and 18 electrons make an ion with a -1 charge.

1s22s22p6 1s22s22p63s2

3p6