Atomic structure

Question 1

What is an atom?

Answer 1

An atom is the smallest part of
an element that can exist. Atoms of each element are represented by a chemical symbol, eg
O represents an atom of oxygen, Na represents an atom of sodium.

Question 2

what is a compound?

Answer 2

Compounds are formed from elements by chemical reactions.
Chemical reactions always involve the formation of one or more new substances, and often involve a detectable energy change.
Compounds contain two or more elements chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they were formed.
Compounds can only be separated into elements by chemical reactions

Question 3

what is a mixture?

Answer 3

A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged.

Question 4

how can mixtures be separated? (go over these using videos and posters)

Answer 4

Mixtures can be separated by physical processes such as filtration, crystallisation, simple distillation, fractional distillation and chromatography. These physical processes do not involve chemical reactions and no new substances are made

Question 5

what was theory before the discovery of the electrons?

Answer 5

Before the discovery of the electron, atoms were thought to be tiny spheres that could not be divided.

Question 6

What was the plum pudding model?

Answer 6

The plum pudding model suggested that the atom is a ball of positive charge with negative electrons embedded in it. - J.J Thompson 1904

Question 7

What was the gold alpha particle experiment?

Answer 7

The results from the alpha particle scattering experiment led to the
conclusion that the mass of an atom was concentrated at the centre
(nucleus) and that the nucleus was charged

Question 8

What was Neil Bohr’s theory?

Answer 8

Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances. The theoretical calculations of Bohr agreed with experimental observations

Question 9

What did James Chadwick do?

Answer 9

Later experiments led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge.
The name proton was given to these particles.
The experimental work of James Chadwick provided the evidence to show the existence of neutrons within the nucleus. This was about 20 years after the nucleus became an accepted scientific
idea.

Question 10

What is relative charge of an electron?

Answer 10

-1

Question 11

what is the relative charge of a proton?

Answer 11

+1

Question 12

what is the relative charge of a neutron?

Answer 12

0

Question 13

What is the atomic number?

Answer 13

The number of protons in an atom of an element is its atomic number. All atoms of a particular element have the same number of protons. Atoms of different elements have different numbers of
protons.

Question 14

relative mass of a proton

Answer 14

1

Question 15

relative mass of a neutron

Answer 15

1

Question 16

relative mass of an electron

Answer 16

very small

Question 17

what is a mass number?

Answer 17

The sum of the protons and neutrons in an atom is its mass number

Question 18

what is an isotope?

Answer 18

Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element.

Question 19

What is the relative atomic mass?

Answer 19

The relative atomic mass of an element is an average value that takes account of the abundance of the isotopes of the element.

Question 20

How is the periodic table arranged?

Answer 20

The elements in the periodic table are arranged 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 21

what do elements in the same group have?

Answer 21

Elements in the same group in the periodic table have the same number of electrons in their outer shell (outer electrons) and this gives them similar chemical properties.

Question 22

How was the periodic table originally arranged?

Answer 22

Before the discovery of protons, neutrons and electrons, scientists attempted to classify the elements by arranging them in order of their atomic weights.

Question 23

Why were the early periodic tables incomplete?

Answer 23

The early periodic tables were incomplete and some elements were placed in inappropriate groups if the strict order of atomic weights was followed.

Question 24

How did Mendeleev impact periodic tables?

Answer 24

Mendeleev overcame some of the problems by leaving gaps for elements that he thought had not been discovered and in some places changed the order based on atomic weights.
Elements with properties predicted by Mendeleev were discovered and filled the gaps.
Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always
correct.

Question 25

what are Elements that react to form positive ions?

Answer 25

metals

Question 26

what are Elements that do not form positive ions

Answer 26

non-metals

Question 27

what are properties of Group 0 elements?

Answer 27

They are unreactive and do not easily form molecules
because their atoms have stable arrangements of electrons. The noble gases have eight electrons in their outer shell, except for helium, which has only two electrons. The boiling points of the noble gases increase with increasing relative atomic mass (going down the group).

Question 28

properties of Group 1 metals

Answer 28

The elements in Group 1 of the periodic table are known as the alkali metals and have characteristic properties because of the single electron in their outer shell. In Group 1, the reactivity of the elements increases going down the group.

Question 29

Group 7 properties

Answer 29

halogens have similar reactions because they all have seven electrons in their outer shell. The halogens are non-metals and consist of molecules made of pairs of atoms. In Group 7, the further down the group an element is the higher its relative molecular mass, melting point and boiling point.
In Group 7, the reactivity of the elements decreases going down the group.
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt