Chemistry Flashcards
Structure of an atom
An atom has a central nucleus. This is surrounded by electrons arranged in shells.
Electron
Negative charge and very small
Proton
Positive charge and same size as neutron
Neutron
Neural charge and same size as proton
Where is the majority of mass of an atom located?
Nucleus
Atomic Number
The number of protons (smaller number)
Mass number
The number of protons and neutrons (bigger number)
Isotope
Same number of protons and electrons but different number of neutrons
Concept of relative atomic mass
Weighted mean of masses of the atoms of isotopes.
Calculating Ar
Total mass of atoms/Total percentage
Where are periods?
Horizontal rows
Where are groups?
Vertical columns
How are elements ordered?
In order of increasing atomic number
Group 1
Alkali metals
Group 2
Alkaline earth metals
Group 16
Common non-metals
Group 17
Halogens
Group 18
Noble gases
Transition metal properties
Conduct electricity in solid and liquid states
Shiny when freshly cut
Transition metals compared to group 1 metals
Higher melting points
Higher density
Greater strength
Greater hardness
Electron configuration
Atomic number (protons)
What happens down a metal group?
Reactivity increases
What happens down a non-metal group?
Reactivity decreases
What do elements in the same group have in common?
Similar chemical properties
Can the nuclei be created or destroyed?
No
State symbol (S)
Solid
State symbol (L)
Liquid
State symbol (G)
Gas
State symbol (AQ)
Aqueous solution
What is an equilibrium?
A situation where forward and back reactions happen at the same rate, and the concentration of substances stay the same.
Factors that affect equilibrium
Concentration of reactants/products
Temperature
Overall pressure
How do you use Ar to work out Mr? Use CO2 as an example
Example CO2:
Ar of C = 12 | Ar of O = 16
12+16+16 = 44
Mr of CO2 = 44
What is Avogadro’s number?
The number of particles in one mole of a substance
What value is Avogadro’s constant?
6.02 x 10^23
What is one mole of a substance?
Ar or Mr in grams
How to work out percentage composition?
Total Ar of element/Mr of compound
x100
What is empirical formula?
Simplest integer ratio of atoms
Conditions for ideal gas
One mole of gas occupies a set volume at a given temperature or pressure. (24dm^3)
What is concentration measured in?
mol dm ^-3 or g dm^-3
Saturated Solution
A solution that contains the maximum amount of solute taht is capable of being dissolved.
Titration calulations
Watch youtube video
Percentage yield
Actual yield(g)/Predicted yield(g)
X100Oxidation
Gain of oxygen
Reduction
Removal of oxygen
Oxidation in terms of electron
Gain of electrons
Reduction in terms of electron
Removal of electrons
How to identify oxidation only?
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How to identify reduction only?
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How to identify a redox (both oxidation and reduction) ?
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How to identify a non-oxidation/reduction?
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Oxidising agent
Normally non-metal or positive ion
Reducing agent
Normally metal or negative ion
Element
A substance that only has one type of atom and it cannot be broken down into anything simpler
Compound
A substance made up of 2 or more elements chemically bonded
Mixture
Consists of 2 or more substances, not chemically bonded
What do atoms often react to form?
Compounds that have an election configuration of a noble gas (group 18)
Ionic bonding
Metals and non-metals reacting leading to electrons going from metals to non-metals.
Anion
Gains electrons and becomes negatively charged
Cation
Loses electrons and becomes positively charged
NH4+
Ammonium
Ca2+
Calcium
Na+
Sodium
Pb2+
Lead
OH-
Hydroxide
NO3-
Nitrate
CO3^2-
Carbonate
SO4^2-
Sulfate
What do roman numerals after an element suggest?
When an element has more than 1 oxidation state, the roman numerals denote which is present e.g. iron (lll)
Physical properties of Ionic compounds
High boiling and melting points
Solid at room temp
Cannot conduct electricity in solid state
Can conduct in molten or in solution state
Strong electrostatic forces
Hard and brittle
Covalent bonding
Bonding between 2 non-metals (sharing of electrons)
Covalent molecules can be…
Small molecules or giant structures
Small covalent molecules
Water (H20)
Ammonia (NH3)
Methane (CH4)
Giant covalent structures
Diamond (C)
Graphite (C)
Silicon dioxide (SiO2)
Physical properties of small covalent molecules
Low melting and boiling points
Does not conduct electricity
(Strong covalent bonds, weak intermolecular forces)
Physical properties of giant covalent properties
Very high melting points
Variable electricity conductivity (Diamond doesn’t, graphite does and silicon is midway)
Metallic bonding
The strong electrostatic force of attraction between metal ions
What do solid metals exist as?
Solid metals exist as a giant structure of positively charged ions surrounded by delocalised electrons.
Physical properties of metals
Shiny High melting and boiling points Good conductor of heat and electricity High density Malleable and ductile
Where are intermolecular forces and how do you overcome them?
They exist between molecules and must be overcome in melting and boiling.
Physical and chemical properties of alkali metals (group 1)
Physical - soft (can be cut with a knife) and low melting points
Chemical -
