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chemistry > key concepts > Flashcards

key concepts Flashcards

1
Q

what are the 4 state symbols

A

s - solid
l - liquid
g - gas
aq- aqueous

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2
Q

what is the formula of water

A

H2O

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3
Q

what is the formula of ammonia

A

NH3

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4
Q

what is the formula of carbon dioxide

A

CO2

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5
Q

what is the formula of hydrogen

A

H2

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6
Q

what is the formula of chlorine

A

CL2

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7
Q

what is the formula of oxygen

A

O2

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8
Q

what is the formula of ammonium

A

NH4+

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9
Q

what is the formula of hydroxide

A

OH-

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10
Q

what is the formula of nitrate

A

NO3-

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11
Q

what is the formula of carbonate

A

CO3 2-

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12
Q

what is the formula of sulphate

A

SO4 2-

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13
Q

common hazard symbols

A

oxidising
environmental hazard
toxic
harmful
highly flammable
corrosive

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14
Q

how did John Dalton describe atoms

A

as solid spheres

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15
Q

what did J J Thomson conclude

A

atoms were not spheres - idea of solid sphere had to change (plum pudding)

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16
Q

what did Rutherford conduct? and how?

A

gold foil experiment - fired positively charged alpha particles at an extremely thin sheet of gold

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17
Q

how did he disprove the plum pudding model could not be right?

A

they were expecting particles to pass straight through or be slightly deflected at most, but most of the particles did go straight through, however, some defective more than expected, and a small number were deflected backwards

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18
Q

what did Rutherford then come up with

A

the nuclear atom - atom we know today.

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19
Q

explain the bohr model

A
  • electrons around nucleus of atom
  • electrons in fixed orbit : nowhere between
  • each cell has a fixed energy
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20
Q

how are scientific models backed up

A

peer review

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21
Q

mass & charge on a proton

A

mass: 1
charge: +1

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22
Q

mass and charge on a neutron

A

mass: 1
charge: 0

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23
Q

mass and charge on a electron

A

mass: 0.0005
charge: -1

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24
Q

facts about the nucleus of a atom

A
  • middle of atom
  • contains protons and neutrons
  • positive charge
  • nucleus is tiny compared to size of atom
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25
Q

facts about the electrons of the atom

A
  • move around the nucleus in electron shells
  • negatively charged
  • tiny & shells cover a lot of space
  • tiny mass
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26
Q

facts about atoms

A
  • neutral (same number of protons and electrons)

however in ions:
- doesn’t have a equal amount of electrons meaning it has a overall charge (negative or positive)

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27
Q

which number on a symbol is the atomic

A

bottom

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28
Q

which number on a symbol is the mass number

A

top

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29
Q

23
Na which is the atomic number which is
11 mass number

A

atomic: 11
mass: 23

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30
Q

what does the atomic number tell you

A

number of protons

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31
Q

what does the mass number tell you

A

total number of protons and neutrons

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32
Q

how to find out how many neutrons are in the element

A

atomic - mass number

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33
Q

what are isotopes

A

different forms of the same element - same number of protons different number of neutrons which means they have the same atomic number but different mass number

34
Q

what is the relative atomic mass

A

Average mass of one atom of the element compared to 1/12 of the mass of one atom

35
Q

how to work out isotopic abundance

A

multiple each relative atomic mass by its isotope abundance and add up the results.
then divide the sum by the abundances

36
Q

who made the first periodic table

A

Dmitri Medeleev

37
Q

facts about Mendeleev’s table

A
  • arranged around 50 elements
  • sorted by properties
  • put elements with similar chemical properties in columns
  • he left gaps for undiscovered elements which he didn’t know yet for future people to fill in
38
Q

facts about todays periodic table

A
  • order of ascending atomic number
  • similar chemical properties for columns called groups
  • groups = number of electrons
  • rows are called periods
  • period = number of shells of electrons
39
Q

what is a atoms electronic configuration

A

2,8,8

40
Q

how to work out the electronic configuration

A

by atomic number

or

number of electrons in outer shell

41
Q

what is a ion

A

a charged particle - can be single atoms or group of atoms

42
Q

what is a negative ion called

A

anions

43
Q

what does a negative ion do

A

gains electrons - more electrons than protons

44
Q

what is a positive ion called

A

cations

45
Q

what does a positive ion do

A

lose electrons - more protons than electrons

46
Q

what groups most likely form ions

A

1 & 2
6 & 7

47
Q

what do groups 1&2 do (ions)

A

lose electrons to form positive ions as they are metals

48
Q

what do groups 6&7 do (ions)

A

gain electrons to form negative ions as they are non-metals

49
Q

how do you work out the formula of a ionic compound

A

write the formulas for the elements

the overall charge must be 0 so work put the ratio that gives a overall neutral charge

50
Q

what happens during ionic bonding?

A

when a metal or a nonmetal react together, the metal atom loses electrons to form a positive ion (cation) and the nonmetals gain these electrons to form a negative ion (anion). These oppositely charged ions are strongly attracted to one another, by electrostatic forces, this attraction is called an ionic bond.

51
Q

how can ionic compounds formed be show

A

dot - cross diagram

52
Q

what is a dot cross diagram

A

shows the arrangement of electrons in a atom or ion.
each electron is represented by a dot or a cross.
so these diagrams can show which atom the electrons in an ion originally came from.

53
Q

what structure do ionic compounds have

A

regular lattice structure

54
Q

what holds ionic compounds together

A

strong electrostatic forces of attraction between oppositely shafted ions, in all directions

55
Q

what are the properties of ionic compounds

A
  • high melting point and boiling point due to strong attraction, takes a lot of energy to break it
  • don’t conduct electricity
  • dissolve easy in water
56
Q

3 types of models for ionic compounds

A

2D
dot cross diagram
3D models

all have advantages and disadvantages

57
Q

what is a covalent bond

A

A strong bond that forms when a pair of electrons is shared between two atoms

58
Q

how small are simple molecules

A

tiny

59
Q

properties of simple molecular substances

A
  • very strong covalent bonds
  • melting and boiling points are low
  • gas or liquid at room temp
  • don’t conduct electricity
60
Q

what is a polymer

A

molecules made up of long chains of covalently bonded carbon ions

61
Q

properties of giant covalent structures

A
  • bonded by strong covalent bonds
  • high melting and boiling point
  • don’t conduct electricity
  • aren’t soluble in water
62
Q

3 examples of giant covalent structures

A

diamond
graphite
graphene

63
Q

features of diamond (giant covalent)

A

-made up of a network of carbon atoms that each form four covalent bonds
-strong covalent bonds, so diamond have a high melting point
-rigid lattice structure
-doesn’t conduct electricity

64
Q

features of graphite (giant covalent)

A

-only forms three covalent bonds
-no covalent bonds: held together weakly (free to move around)
-high melting point
-conducts electricity

65
Q

features of graphene (giant covalent)

A

-one atom thick
-sheet of carbon atoms joined together in hexagons

66
Q

facts about metallic bonding

A

-giant structure
-electrons in outer shell are delocalised
-metallic bonding is very strong
-metallic bonding includes metallic elements and alloys

67
Q

metallic bonding properties

A

-very high melting and boiling points
-aren’t soluble in water
-shiny solids at room temp
-atoms slide over eachother, therefore they are malleable
-good conductors of electricity and heat

68
Q

difference between metals and non metals

A

-metals have metallic bonding non-metals dont
-different chemical properties
-non metals are more dull looking, metals are more shiny

69
Q

what is mass

A

always conserved

70
Q

what happens during a chemical reaction

A

no atoms destroyed
no atoms created

71
Q

how to work out relative formula mass

A

use the periodic table to find relative atomic mass
add up relative atomic masses of all the atoms
if there’s a small number it means there 2 of everything inside the brackets

72
Q

how to work out the empirical formula

A

start by finding the Mr of the empirical formula
divide by the Mr of the compound by the Mr of the empirical formula
to get the formula, multiple everything by the empirical formula

73
Q

what is a mole

A

one mole of atoms or molecules of any substance will have a mass in grams equal to the relative particle mass for that substance

74
Q

how to work out the number of moles

A

mass in grams/ Mr of compound

75
Q

how to workout mass

A

moles x Mr

76
Q

how to work out concentration

A

mass of solute / volume of solution

77
Q

how to work out mass

A

concentration x Mr

78
Q

how to calculate empirical formula from mass

A

-work out how many moles of each element you have
-work out the smallest whole number ratio to get empirical formula

79
Q

how to calculate mass of a product from limiting reactant

A

-balance the equ
-work out relative formula mass
-find how many moles there are
-use balanced equ to work out how many moles there will be of the other substance
-use the number of moles to calculate mass

80
Q

how can you balance equations using reacting masses

A
  1. divided the mass of each substance by its relative formula mass to find the number of moles
  2. divide the number of moles by the same amount to make them all numbers
  3. multiple all numbers by the same amount to make them all whole numbers
  4. write the balanced equ for the reaction
81
Q

work out limiting reactants

A
  1. divide the mass of each substance to find the moles
  2. divide by the smallest number of moles
  3. compare the ratios between the moles of products with the balanced equ

chemistry (7 decks)

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