Atomic Structure ⚛️

Question 1

What are the three ideas in John Dalton’s theory about the atom?

Answer 1

• Atoms cannot be created, divided or destroyed.
• Atoms of the same element are exactly the same and atoms of different elements are different.
• Atoms join.with other atoms to make new substances.

Question 2

What discovery caused the original Dalton model of an atom to change?

Answer 2

The discovery of subatomic particles.

Question 3

Describe the atomic model proposed by JJ Thomson?

Answer 3

Plum pudding model.
Negatively charged electrons scattered through a positively charged material.

Question 4

Describe Rutherford’s new model of the atom.

Answer 4

• Mass concentrated in the central nucleus
• Mostly empty space.
• Electrons travel in random paths around the nucleus.

Question 5

Describe the structure of an atom.

Answer 5

• Small central nucleus made up of protons and neutrons.
• Electrons orbit (move around) the nucleus in shells.

Question 6

What is the radius of the nucleus? How large is it compared to the radium of an atom?

Answer 6

The radius of the nucleus is 1x10 to the -14 m. This is 1/10000 of the atomic radius.

Question 7

What does the atomic number of an atom represent?

Answer 7

The number of protons.

Question 8

Fill in the blank: ‘Atoms of the same element have the same number of _________ in the nucleus and this is unique to the element’

Answer 8

Protons

Question 9

What is an isotope?

Answer 9

Isotopes are atoms with the same number of protons (so they are the same element) but a different number of neutrons.
Isotopes of an element have the same atomic number but different mass numbers.

Question 10

Boron has the atomic number 5 and the mass number 11. How many protons, electrons and neutrons does Boron have?

Answer 10

5 protons
5 electrons
6 neutrons

Question 11

How did Mendeleev arrange in the elements in his periodic table?

Answer 11

• Elements arranged with increasing atomic masses.
• Elements with similar properties but into groups (due to periodic trends in chemical properties)
• Switched the position of some elements.
• Gaps left for undiscovered elements.

Question 12

How was Mendeleev able to predict the properties of new elements?

Answer 12

Mendeleev left gaps in his periodic table. He used the properties of elements next to these gaps to predict the properties of undiscovered elements.

Question 13

How are elements arranged in the modern periodic table?

Answer 13

In order of increasing atomic number.

Question 14

Fill in the black: ‘Elements in the same group (column) have similar ________ ________’

Answer 14

Chemical properties

Question 15

Why do elements in the same column have similar chemical properties?

Answer 15

Same number of outer shell electrons.
Number of outer shell electrons determines how an atom reacts.

Question 16

What does the period (row) number tell you about all the elements in that period?

Answer 16

Elements in the same period have the same number of electron shells.
E.g all elements in period 4 have 4 shells of electrons

Question 17

What does group (column) number tell you about all the elements in that group?

Answer 17

All elements in the same group have the same number of outer electrons.
E.g all elements in group 2 have 2 electrons in their outer shell.

Question 18

What is the maximum number of electrons allowed in each of the first 3 shells?

Answer 18

2, 8, 8

Question 19

When are atoms most stable?

Answer 19

When they have full electron shells.

Question 20

The atomic number of Na is 11.
What is the electron configuration of Na?

Answer 20

2, 8, 1

Question 21

How is the electron configuration of an element related to its position in the periodic table?

Answer 21

The number of rings is the period
The number of electrons in the outer ring is the group
The total number of electrons is the atomic number