atomic mass

• Natuurkunde / Scheikunde
• Middelbare school
• vwo
• Leerjaar 2

Ch 3.3 atomic mass

Molucular mass (u)

percentage by mass

Elements, molecules and compounds

H₂ = molecule of an element. 

It is made up of only H-atoms.

CH₄ = molecule of a compound. 

It is made up of C and H atoms.

      C & H are (non-metal) atoms that are chemically combined

Hydrogen is an element.

1. true
2. false

Which of the following elements are metals? (use p 196)

1. Fluor
2. Nickel
3. Platinum
4. Sulpher

Lesson goals:

At the end of the lesson I can find in the periodic table:

- how many protons and electrons are in an element;

- what the atomic mass of an element is;

- how many neutrons are in an element;

- if an element is a metal or not. 

I can calculate:

- atomic mass, molecular mass and % by mass of an element in a molecule

https:

There are seven elements which always form molecules with two of their atoms. These are the BrINClHOF substances 

(Br, I, N, Cl, H, O, and F) 

Atoms, protons, neutrons and electrons

Atomic number = number of the element in the periodic table.

Atomic mass = number of protons + number of neutrons

14                                 

                                  

7                                  

Atomic number = 7

Atomic mass = 14 u

Number of protons = 7

Number of neutrons = 14 - 7 = 7

Number of electrons = 7

N

The atomic mass of sodium is?

1. 11 u
2. 12 u
3. 23 u
4. 34 u

How many protons has sodium ?

1. 11
2. 12
3. 23
4. 34

How many neutrons has sodium ?

The number of neutrons = atomic mass - number of protons = 23 - 11 = 12

1. 11
2. 12
3. 23
4. 34

What is the atomic mass of carbon?
(book p. 86)

The atomic mass of Carbon 14,0.

Molecular mass

Molecular mass is the total mass of a compound.

NH₃ has a molecular mass of 

1 x N = 14 u

3 x H = 3 x 1 u  +

 NH₃ = 17 u

Calculate the molecular mass of aspirin (C₉H₈O₄).

C = 14       9 x 12 =108 u 

H = 1           8 x 1 =    8 u

O = 16      4 x 16 = 64 u +

                               180 u

Lesson goals:

At the end of the lesson I can find in the periodic table:

- how many protons and electrons are in an element;

- what the atomic mass of an element is;

- how many neutrons are in an element;

- if an element is a metal or not. 

I can calculate:

- atomic mass, molecular mass and % by mass of an element in a molecule

Questions?