Key concepts.1 Flashcards Preview

CHEMISTRY > Key concepts.1 > Flashcards

Flashcards in Key concepts.1 Deck (47):
1

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

1803 Dalton
Solid atom model : all atoms of an element are identical; different elements have different atoms

1897 Thomson
Discovers the electron

1904 Thomson
Plum pudding model : atoms are spheres of positive charge with negative electrons dotted around inside

1911 Rutherford
Solar system model: atoms have a positive nucleus surrounded by negative electrons in orbits

1913 Bohr
Electrons shell model: electrons occupy shells or energy levels around the nucleus

1918 Rutherford
Proton discovery

1932 Chadwick
Neutron discovery

2

Structure of the atom

Nucleus containing protons and neutrons

Surrounded by electrons in shells

3

Relative charge and mass of a proton

Charge is +1
Mass is 1

4

Relative charge and mass of a neutron

Relative charge = 0
Relative mass = 1

5

Relative charge and mass of and electron

Relative charge = -1
Relative mass = 0.0005 or 1/1836

6

Why do atoms have equal numbers of protons and electrons

By definition, atoms have no overall electrical charge. That means that there must be a balance between the positively charged protons and the negatively charged electrons. Atoms must have equal numbers of protons and electrons.
Neutral overall

7

What’s the size of the nucleus compared to the atom

Very small

8

Where is most the mass in an atom

Concentrated in the nucleus

9

Define mass number of an atom

The mass number (symbol A, from the German word Atomgewichte (atomic weight), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus.

10

If several atoms have the same number of protons what does this mean?

It’s the same element and this number is unique to this element

11

What’s an isotope

Different atoms of the same element containing the

Same no of protons

Different no of neutrons in their nuclei

12

Atomic number =

Number of protons

13

Mass number =

Protons + neutrons

14

How does the existence of isotopes result in relative atomic masses of some elements not being whole numbers

X

15

How would you calculate the relative atomic mass of an element from the relative masses and abundance’s of its isotopes

Multiply the mass number of each isotope by its relative abundance and then add them all together and divide by 100

16

Gallium has two isotopes gallium-69 and gallium-71
Relative abundance of gallium-69 is 60% calculate the relative atomic mass of gallium

Relative abundance of gallium-71
= 100%-60%=40%

Relative atomic mass = (69x60) + (71x40)/100
= 4140 + 2840/100

= 69.8

17

Describe how medeleev arranged the elements, known at that time in a periodic table using properties of these elements and their compounds

1869

Order of relative atomic masses
Checked properties of element and compounds
Swapped places of some so that elements with similar properties lined up
Left gaps where he thought there were other elements and predicted there properties
When these were discovered Mendeleev predictions fitted the properties very well

18

Mendeleev thought he had arranged elements in order of increasing atomic mass why was this not always true?

The positions of elements in some pairs were reversed
Because some of the relative abundance of istotopes of some pairs of elements in the periodic table

19

How are elements arranged in the periodic table now

In order of increasing atomic number

20

Rows are called

Periods

21

Vertical columns are called

Groups

22

Where are elements with similar properties placed

In same groups/vertical columns

23

Group 6 elements

Don’t react with water

All react with oxygen except oxygen

All from compound with hydrogen with the general formula: H2X

6 electrons in their atoms outer shell

24

Group 7 elements

All react with water

Don’t react with oxygen

All from compounds with hydrogen with the general formula : HX

7 electrons in their atoms outer shell

25

Where are metals on the periodic table

On the left hand side and in the centre

26

Where are non metals

On the right hand side

27

Where’s the split between metals and non metals in the periodic table

Underneath B Si As Te At in s disginal lime

28

Explain the division between non metals and metals in terms of the atomic structure of the elements

X

29

What’s the number of electrons in the outer shell the same as

The group number that it’s in

30

What does the period number relate to

The amount of shells within the elements in the periods

31

Elements in groups have the same number of

Electrons in their outer shell except for helium in group 0

32

How are ionic bonds formed

By the transfer of electrons between atoms to produce actions and anions

33

What is an ion?

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

34

What’s a cation

Positively charged ion

Formed when an atom or foul of atoms loses one or more electrons

35

What cations usually form from?

Hydrogen or metals

36

How many electrons do group 1 atoms lose?

1 electron to form ions with one positive charge

37

What’s ana noon

A negatively charged ion

38

When are Anions formed

When an atom or group of atoms gains one or more electrons

39

What are anions usually formed from

Non- metals

40

What happens to group 7 atoms regarding gaining or losing electrons

Then gain 1 electron to form ions with one negative charge

41

What does an ions name depend on?

The charge and wether the ion also contains oxygen

42

What do compound ions contain

Atoms of two different elements

43

Positively charged ions are formed from? And what do they take the name of

Formed from hydrogen or metal atoms and they take the name of the element

44

Negatively charged ions are formed from SINGLE non - metal atoms take the name of the element but end in...

-ide

45

Negatively charged ions in COMPOUNDS containing THREE OR MORE elements, one of which is oxygen end in ...

-ate

46

What’s the only formula which doesn’t follow the -ate rule

OH-

47

Check on balancing charges

If there different charges multiply them
If there the same they cancel out