Atomic structure and the Periodic Table

Question 1

Name 4 physical separation techniques used to separate MIXTURES.

Answer 1

1. Filtration
2. Crystallisation
3. Distillation
4. Chromatography

Question 2

What is filtration used for?

Answer 2

Separating an INSOLUBLE SOLID from a LIQUID.

Question 3

What is crystallisation used for?

Answer 3

Separating a SOLUBLE SOLID from a LIQUID.

Question 4

What is simple distillation used for?

Answer 4

Separating a LIQUID from a SOLID if we want to keep the LIQUID.

Question 5

What is fractional distillation used for?

Answer 5

Separating a mixture of different liquids, that have different boiling points.

Question 6

What is paper chromatography used for?

Answer 6

Separating substances based on their different SOLUBILITIES.

Question 7

What is the paper in chromatography also known as?

Answer 7

The STATIONARY phase as it does not move.

Question 8

What is the solvent in chromatography also known as?

Answer 8

The MOBILE phase as it does move.

Question 9

Why does paper chromatography work?

Answer 9

Because each chemical in the mixture will be ATTRACTED to the stationary phase to a DIFFERENT EXTENT.

Question 10

What will happen to chemicals that are strongly attracted to the stationary phase?

Answer 10

They will NOT move very far up the paper.

Question 11

What will happen to chemicals that are weakly attracted to the stationary phase?

Answer 11

They WILL move further up the paper.

Question 12

What will a pure chemical always produce in all solvents?

Answer 12

A single spot.

Question 13

Why do we draw our starting line in pencil?

Answer 13

If we drew the line in pen, the pen ink would MOVE UP the paper WITH the SOLVENT.

Question 14

What is the radius of an atom?

Answer 14

………-10

1 x 10 m ( 0.1 nm)

Question 15

What is the radius of the nucleus?

Answer 15

……….-14

1 x 10 m ( less than 1/10 000 of that of the atom)

Question 16

Who discovered the electron?

Answer 16

J.J Thomson in 1897.

Question 17

What is the plum pudding model?

Answer 17

It suggested that the atom is a ball of positive charge with negative electrons embedded in it.

Question 18

What did the results from the alpha particle scattering experiment show?

Answer 18

That the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged. This nuclear model replaced the plum pudding model.

Question 19

How did Niels Bohr adapt the nuclear model?

Answer 19

He suggested that electrons orbit the nucleus at specific distances.

The theoretical calculations of Bohr agreed with experimental observations.

Question 20

Who discovered the neutron?

Answer 20

James Chadwick.

Question 21

What is an isotope?

Answer 21

Atoms of the same element with different number of neutrons but the same number of protons.

Question 22

What is the relative atomic mass of an element?

Answer 22

It is an average value that takes account of the abundance of the isotopes of the element.

Question 23

How are elements arranged in the periodic table?

Answer 23

In order of atomic (proton) number and so that elements with similar properties are in columns, known as groups.

The table is called a periodic table because similar properties occur at regular intervals.

Question 24

Before the discovery of protons, neutrons and electrons, how did scientists calssify the elements?

Answer 24

By arranging them in order of their atomic weights.

Question 25

How did Mendeleev overcome some of the problems with the early periodic table?

Answer 25

By leaving **gaps** for elements that he thought had **not** been **discovered**.

Question 26

What are the elements in Group 0 of the periodic table called?

Answer 26

The **noble gases**. ## Footnote They are **unreactive** and do **not easily** form **molecules** because their atoms have **stable arrangements** of electrons.

Question 27

How does the boiling point of the noble gases change as you go down the group?

Answer 27

**Increases** with increasing **relative atomic mass** (going **down** the **group**).

Question 28

What are the elements in Group 1 of the periodic table known as?

Answer 28

**Alkali metals**. ## Footnote They have characteristic properties because of the single electron in their outer shell.

Question 29

What are the Group 7 elements of the periodic table known as?

Answer 29

**Halogens**. ## Footnote They have **similar reactions** because they all have **seven electrons** in their **outer shell**. They are **non-metals** and consist of molecules made of **pairs of atoms.**

Question 30

How does the relative molecular mass, melting and boiling point change as you go down the group of the halogens?

Answer 30

It **increases**.

Question 31

How does the reactivity of the elements change as you go down group 7.

Answer 31

It **decreases**.

Question 32

Give two advatnages of using modern symbols rather than Dalton's symbols.

Answer 32

Any two from: * doesnt show how many atoms present * more difficult to remeber symbol for each element * modern symbols are based on name of element

Question 33

What does volatile mean?

Answer 33

Easily evaporated at normal temperatures.

Question 34

Explain how scientists used the results from alpha particle scattering experiment to: * disprove the plum pudding model * give evidence for the nuclear model

Answer 34

* According to plum pudding model alpha particles should go straight through. However, some alpha particles were deflected. * Evidence fro nuclear model was that positive particles deflected and repelled so must be a dense positive center of atom.

Question 35

Explain the trend in reactivity of group 1 metals with water.

Answer 35

* Outer shell electron futher from the nucleus * Outer electron less tightly held by nucleus * Outer shell electron more easily lost

Question 36

What is the state of iodnine at 25°C

Answer 36

solid

Question 37

The relative formula mass of chlorine is 35.5 Explain why this is not a whole number

Answer 37

Because it is an average.