Atomic Structure, the periodic table, history of atoms

Question 1

What does the periodic table show and how is it structured?

Answer 1

It shows all elements discovered
1st version by Mendeleev- he arranged elements with similar properties into vertical columns
Vertical columns called groups
Horizontal rows called periods

Question 2

What are the numbers by each symbol?

Answer 2

Atomic number and mass number

Oxygen has 8 protons and 8 neutrons and 8 electrons - mass number is 8

Question 3

Explain electron arrangement?

Answer 3

Electrons are arranged in energy levels called shells
These orbit the nucleus
Represented by crosses
Very small compared to protons and neutrons

Question 4

What is the maximum number of electrons in each shell?

And how do you draw the shells?

Answer 4

1st shell maximum- 2
2nd shell- 8
3rd shell- 8
4rth shell -  2
The shells start from the nucleus and fill up outwards

Question 5

What are isotopes?

Answer 5

Isotopes are elements with the same number of protons and electrons but different number of neutrons
So they have different atomic numbers

Question 6

How do you work out relative atomic mass?

Answer 6

This figure is used because many elements exist as a different number of isotopes so this is more useful than mass number

It is the average mass taking into account all the masses and amounts of the isotopes

Question 7

Draw electron configurations of first 20 elements

Answer 7

Hydrogen to calcium

Question 8

What are the significant models used for atoms and theory of atomic structure?
What was the plum pudding?

Answer 8

John Dalton - atoms are solid spheres and different spheres make up different elements
Thompson said not solid spheres - atom must contain negative particles called electrons
This was plum pudding showing atom as a ball of positive charge with negative electrons stuck in it

Question 9

What is the difference between plum pudding and nuclear model of atom?

Answer 9

Rutherford said plum pudding wrong
He fired alpha particles at thin sheet of gold
Some particles deflected straight back
Plum Pudding not right because expected to pass right through
Rutherford said nuclear atom - if particles hit nucleus they deflect but most go through the space between nucleus and electrons

Question 10

What are the three subatomic particles and explain their role in the atom?

Answer 10

Protons - +ve charge, heavy in nucleus so nucleus has +ve charge
Neutrons - heavy and neutral in nucleus
Electrons - negative charge, move around nucleus in shells, orbit volume determines size of atom, virtually no mass
Atoms are neutral because protons and electrons equal, charges cancel out
In ion number of protons doesn’t equal number of electrons so has overall charge

Question 11

What is atomic number and mass number?

Answer 11

Nuclear symbol tells atomic and mass number
Atomic number tells how many protons
Mass number tells total of protons and neutrons in the atom
To get neutron number subtract atomic number from mass number