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Chemistry IGCSE > Unit 2 - atoms, elements and compounds > Flashcards

Unit 2 - atoms, elements and compounds Flashcards

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1
Q

Element

A

A substance that can’t be broken down into anything simpler using a chemical reaction - only have 1 type of atom and each is unique

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2
Q

Compound

A

Formed when one or more atoms of different elements are joined together by chemical reactions

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3
Q

Mixture

A

Formed when two or more substances are found together but not chemically bonded to each other - can be elements or compounds - can be easily separated

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4
Q

Three sub-atomic particles in atoms

A
  • Electrons
  • Neutrons
  • Protons
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5
Q

Location of sub-atomic particles

A
  • Electrons - energy shells
  • Neutrons - in the nucleus
  • Protons - in the nucleus
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6
Q

The nucleus of an atom

A
  • Radius of the nucleus is 10000x smaller than radius of the atom
  • Most of the mass is within the nucleus because protons and neutrons have the most mass
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7
Q

Protons

A
  • Number of protons = proton/atomic number
  • Number of protons determines the element
  • Mass of 1
  • Charge of +1
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8
Q

Neutrons

A
  • Mass of 1
  • Charge of 0
  • Atoms of the same element but different amount of neutrons are isotopes
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9
Q

Electrons

A
  • Smallest sub-atomic particle
  • Mass of 1/2000
  • Charge of -1
  • Orbit the nucleus in shells
  • Number of electrons = number of protons - elements have no charge
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10
Q

Features of elements on the periodic table

A
  • Nucleon/atomic mass number
  • Proton/atomic number
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11
Q

Atomic number

A
  • Also known as proton number
  • Number of protons in an element
  • Shows amount of electrons in the element too
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12
Q

Atomic mass Number

A
  • Also known as nucleon number
  • Number of protons + number of neutrons
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13
Q

Neutron calculation

A

Atomic mass number - Proton number

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14
Q

Electronic configuration

A

The distribution of electrons of an atom or molecule in electron shells

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15
Q

Amount of electrons in each shell

A
  • First shell = Max of 2
  • Second shell = Max of 8
  • Third shell = Max of 8
  • Fourth shell = Max of 18
  • …
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16
Q

How to write electron configuration

A
  • Written in the form x,x,x,
  • Example - Aluminum = 2,8,3
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17
Q

Elements that have full shells and are uncreative

A

Noble gases - Group VIII

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18
Q

Ions

A

Charged atoms

19
Q

What elements have to do to become stable

A
  • Obtain a full outer shell through losing or gaining electrons
20
Q

Ion charges of elements in each group

A
  • Group 1 = 1+
  • Group 2 = 2+
  • Group 3 = 3+
  • Group 4 = 4+-
  • Group 5 = 3-
  • Group 6 = 2-
  • Group 7 = 1-
  • Group 8 = 0
21
Q

Isotopes

A

Atoms with the same number of protons but different numbers of neutrons

22
Q

Nuclear notation

A
  • Mass number on upper-left
  • Atomic number on lower-left
  • Chemical symbol on the right
  • If ion, charge is on upper-right of chemical symbol
23
Q

Calculating average relative atomic mass

A
  • Average Atomic mass = Sum of [(Atomic mass x % abundance)] for each isotope ÷ 100
  • Average Atomic mass = sum of [(atomic mass x relative abundance)] for each isotope ÷ sum of the relative abundance
24
Q

Ionic bonding

A

Occurs between metal and non-metal atoms - metal donates electrons to the non-metal for both to obtain full shells

25
Q

Cations

A
  • Positive ions
  • Donate electrons in bonding
  • Metal atoms in ionic bonding
26
Q

Diagram used for ionic bonding

A

Dot-and-cross diagram

27
Q

Anions

A
  • Negative ions
  • Gain electrons in bonding
  • Non-metal atoms in ionic bonding
28
Q

Suffix for non-metals in ionic bonding

A
  • ide e.g. fluorine –> fluoride
29
Q

Forces keeping together ionic bonds

A

Strong electrostatic forces between positive and negative charged particles

30
Q

Structure made from ionic bonding

A
  • Giant lattice structure held together by strong electrostatic forces of attraction
31
Q

Ionic bonding with incomplete electrons

A
  • If one element can’t donate enough electrons, multiple of the element will be used e.g. lithium and oxygen
32
Q

Properties of ionic compounds

A
  • High melting and boiling points - Higher if there is higher charge since more energy is needed to break bonds and separate ions
  • Conduct electricity molten or dissolved in water to make aqueous solutions, not as solid - ions can freely move molten or dissolved but not as a solid
32
Q

Covalent bonds

A

A bond between two non-metals through the sharing of electrons

33
Q

Rules of covalent bonding

A
  • Both atoms involved must share the same number of electrons
  • The number of electrons shared os qual to the number of electrons needed to fill the outer shell
  • The smallest number of electrons needed are shared
34
Q

Types of covalent bonds

A
  • 1 pair of electrons bonding = single bond
  • 2 pairs of electrons bonding = double bond
  • …
35
Q

Diagram used for covalent bonding

A

Dot-and-Cross diagram

36
Q

Properties of covalent bonds

A
  • Low melting point - for simple covalent molecules - large molecules need more energy and have higher melting points
  • Don’t conduct electricity - don’t have charged particles that can move through the structure
37
Q

Composition of diamond

A
  • Made of only carbon
  • Each carbon shares one electron with four other carbons to make a giant structure
  • Known as a macromolecule
  • Very hard - due to strong covalent bonds in giant structure
  • Used for cutting tools
38
Q

Composition of graphite

A
  • Made of only carbon
  • Each carbon shares one electron with three other carbons, fourth is delocalized
  • Known as a macromolecule
  • Layered hexagonal arrangement held together by weak intermolecular forces - lets layers slide
39
Q

Uses of graphite

A
  • Powder can be added to surfaces of moving parts e.g. engine parts to reduce friction
  • Used as electrodes in a battery
  • Electrical contacts in motors
  • Electrodes in electrolysis
40
Q

Composition of Silicon(IV) oxide

A
  • Each silicon shares an electron with 4 oxygens - forms 4 covalent bonds
  • Each oxygen makes two bonds with silicon atoms
41
Q

Properties of Silicon(IV) oxide

A
  • Forms transparent crystals
  • Very hard - less than Diamond
  • Extremely high melting and boiling points
  • Do not conduct electricity - no delocalized electrons
  • Do not dissolve in water
42
Q

Metallic bonding

A

Electrons form a ‘sea’ of delocalized electrons that surround positive metal ions - held together by strong electrostatic forces of attraction - form giant metal lattice structure

43
Q

Properties of metals

A
  • High melting and boiling points - lots of energy needed to break the bonds of the lattice
  • Conduct electricity - due to presence of delocalized electrons
  • Malleable - layers which can move and slide past each other
  • Ductile - layers can move and slide past each other

Chemistry IGCSE (12 decks)

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