Elements , Compounds And Atoms

Question 1

What are elements?

Answer 1

Substances (made up of only one type of atom) that cannot be broken down into anything simpler

Question 2

What are compounds?

Answer 2

Substances which contain 2 or more elements that are chemically combined

Question 3

How does a mixture differ from a compound?

Answer 3

mixture:
- contains two or more elements or compounds
- not chemically combined
- have the same properties of their components

Question 4

What is a molecule?

Answer 4

two or more atoms chemically joined together

Question 5

What are monatomic elements?

Answer 5

Elements that exist as individual , unbonded atoms , not as molecules (e.g. helium , argon)

Question 6

What are diatomic elements?

Answer 6

Molecules composed of two of the same atom (e.g. hydrogen , oxygen)

Question 7

What are giant aggregates?

Answer 7

Substances where a very large number of atoms are linked together by strong covalent bonds (e.g. diamond , graphite)

Question 8

How can the components from a compound/mixture be produced or separated?

Answer 8

compound - producing an element requires chemical change
mixture - separating components can be done using physical techniques (does not need chemical change)

Question 9

What is an electron ?

Answer 9

A subatomic particle found in shells around the nucleus

Question 10

What are the characteristics of an electron?

Answer 10

-negatively charged
-mass of virtually 0
-found in shells
-can be lost or gained in reactions

Question 11

What is an atom?

Answer 11

The smallest part of a substance that cannot be broken down chemically

Question 12

Describe the structure of an atom

Answer 12

a nucleus containing protons and neutrons surrounded by electrons in shells

Question 13

Why do atoms contain equal numbers of protons and electrons?

Answer 13

to make the atom neutral with an overall charge of zero as protons are positively charged and electrons are negatively charged

Question 14

What is the size of the nucleus compared to the overall size of the atom?

Answer 14

very small

Question 15

Where is most of the mass of an atom concentrated in?

Answer 15

the nucleus

Question 16

What is an ion?

Answer 16

An atom or a group of atoms with a positive or negative charge

Question 17

What is the relative mass and relative charge of a proton?

Answer 17

Relative mass = 1
Relative charge = +1

Question 18

What is the relative mass and relative charge of a neutron?

Answer 18

Relative mass = 1
Relative charge = 0

Question 19

What is the relative mass and relative charge of an electron?

Answer 19

Relative mass = approx 0 (1/1840)
Relative charge = -1

Question 20

What is the atomic number?

Answer 20

The number of protons and (if neutral) electrons in an atom

Question 21

What is the mass number?

Answer 21

The sum of the protons and neutrons

Question 22

what particle is used to determine what element a substance is?

Answer 22

proton

Question 23

What did James Chadwick discover?

Answer 23

Neutrons (NOT protons)

Question 24

Describe the plum pudding model

Answer 24

The plum pudding model is the idea that an atom is a sphere of positive charge with negatively charged electrons scattered through it (using a cathode ray tube)

Question 25

What did Niels Bohr discover?

Answer 25

Electron shells (energy levels)

Question 26

What did Ernest Rutherford discover?

Answer 26

The nuclear model - atoms have a tiny positive nucleus with negatively charged electrons scattered outside it taking up most of its volume (using alpha particles)

Question 27

Describe how the Dalton model of an atom has changed over time because of the discovery of subatomic particles

Answer 27

1 - atoms not being solid balls > lots of space with nucleus and electrons 2 - isotopes > atoms of the same element can have different masses due to neutrons 3 - atoms being divisible > the discovery of negatively charged electrons through the cathode ray tube

Question 28

What are isotopes?

Answer 28

Isotopes are atoms of the same element which have the same number of protons but a different number of neutrons

Question 29

What is the relative atomic mass?

Answer 29

The average mass of an atom (compared to 1/12th the mass of a carbon atom)

Question 30

What effect does having isotopes have on the relative atomic masses of some elements?

Answer 30

not being whole numbers

Question 31

How do work out the relative atomic mass?

Answer 31

By multiplying the mass number of the isotopes with its abundance (in percentage) and dividing it by 100

Question 32

What is the electron arrangement in the energy levels (shells)

Answer 32

2,8,8

Question 33

What is the group number equal to?

Answer 33

The numbers of electrons in the outer shell (column)

Question 34

What is the period number equal to?

Answer 34

The number of shells (row)

Question 35

How many electrons do non-metals have in their outer shell?

Answer 35

more than 4

Question 36

How many electrons do metals have in their outer shell?

Answer 36

less than 4

Question 37

Which group in the periodic table contains the most reactive metals and why?

Answer 37

Group 1 (the alkali metals) They only have to lose one electron to gain a full outer shell (1+ cation)

Question 38

why do elements get more reactive as you go down the periodic table

Answer 38

- the outer electron goes further from the nucleus - the atoms get larger - the attraction between the nucleus and the outer electron gets weaker - the electron is more easily lost

Question 39

What group in the periodic table contains the most reactive non - metals?

Answer 39

Group 7 They only have to gain one electron to gain a full outer shell (1- anion)

Question 40

What are elements in group 7 called?

Answer 40

Halogens

Question 41

What are elements in group 0 called and how does their reactivity change?

Answer 41

Noble gases They only have to gain one electron to gain an outer shell

Question 42

what are the elements found in the central block of the periodic table between group 2 and group 3 called?

Answer 42

transition metals

Question 43

why can hydrogen be placed in either Group 1 or Group 7?

Answer 43

because it only has 1 electron meaning it could: - lose 1 to go in Group 1 - or gain 1 to go in Group 7

Question 44

What would the formation of ions be for elements in group 2 and 6?

Answer 44

Group 2 = 2+ cations Group 6 = 2- anions

Question 45

How many electrons does a sodium ion have compared to a sodium atom?

Answer 45

(Na) would have 11 electrons (Na+) would have 10 electrons as it has a +1 charge