Chemistry Unit 1 Flashcards
Describe how elements are arranged on the periodic table
Elements on the periodic table are arranged by increasing atomic number.
Describe the trends on the periodic table
The position of elements on the Periodic Table allows us to make predictions of their physical properties and chemical behaviour.
Describe the trends on the periodic table along a period
Going along a period, elements move from metallic to non-metallic and add an outer electron each time.
Describe the trends on the periodic table down a group
Going down a group in the periodic table, the elements contain the same number of outer electrons but an extra outer shell each time.
What is a metallic lattice?
Li, Be, Na, Mg, Al, K, Ca
What is a covalent molecular?
H2, N2, O2, F2, Cl2, P4, S8 and fullerenes (eg C60)
What is a covalent network?
B, C (diamond and graphite), Si
What is a monatomic?
Noble gases
What is the covalent radius?
The covalent radius is a measure of the size of an atom.
What does the covalent radius do across and down the periodic table?
Across a period, the covalent radius decreases as the nuclear charge increases. Going down a group, the covalent radius increases as the number of occupied shells increases.
State the definition of the term first ionisation energy
First ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms.
State the definition of the term second ionisation energy
Second ionisation energy is the energy required to remove the 2nd mole of electrons.
Explain the trends in ionisation energy on the periodic table
Across a period, the ionisation energy tends to increase as the nuclear charge increases. Down a group, the ionisation energy decreases due to increased screening effect.
State the definition of the term electronegativity
Electronegativity is a measure of the attraction which an atom has for the electrons in a bond.
Explain the trends in electronegativity on the periodic table going down
Going down a group, the electronegativity decreases due to the screening effect of the inner shell electrons.
Explain the trends in electronegativity on the periodic table going across
Across a period, the electronegativity values increase due to the increasing nuclear charge.
State how covalent bonds are formed
A covalent bond occurs between non-metal elements due to the attraction for the shared pair of electrons.
How are polar covalent bonds formed?
Polar covalent bonds are formed when the attractions of the atoms for the pair of bonding electrons are different.
What happens when polar covalent bonds are formed?
One atom will become delta positive (δ+) and the other delta negative (δ-). The atom with the higher electronegativity will be delta negative (δ-).
What is the spatial arrangement in polar covalent molecules?
Not all substances with polar covalent bonds will be polar molecules due to the spatial arrangement of the atoms.
What does ionic formula show?
Ionic formula shows the simplest ratio of each type of ion and can show the charge of each ion.
Describe the bonding continuum
The bonding continuum shows the ‘continuum’ of states from covalent to ionic bonds.
Type of bonding in room temperature
Covalent networks - solid; Covalent molecular - gas or liquids; Ionic substances - solid.
Type of bonding in melting points
Covalent molecular - low melting points; Covalent network - high melting points; Ionic bonds - high melting points.
What is solubility meaning?
Solubility decreases as molecules increase in size. Polar covalent compounds and ionic substances tend to be soluble in water.
what bonds conduct?
Covalent bonds do not conduct, with the exception of carbon in the form of graphite ionic bonds can conduct when molten or in solution.
State the 3 types of intermolecular (van der Waals) forces
London dispersion forces (LDFs), Permanent dipole-permanent dipole (Pd-Pd) forces, Hydrogen bonding.
How are LDFs formed?
LDFs are formed by the electrostatic attraction between temporary dipoles and induced dipoles.
Why are LDFs always present?
Electrons are continuously moving, leading to LDFs between all atoms and molecules.
LDF characteristics
LDFs are the weakest intermolecular force and get stronger with more electrons.
Explain when a molecule is described as polar
Molecules are polar when they have a permanent dipole.
Describe a permanent dipole-permanent dipole interaction
Dipole-Dipole interaction is the attraction between oppositely charged ends of polar molecules.
Pd-Pd interactions characteristics
Pd-Pd interactions are stronger than LDFs and are in addition to LDFs.
Describe a hydrogen bond
Hydrogen bonds are Pd-Pd interactions found between molecules which contain highly polar bonds.
Where can hydrogen bonds form between?
Hydrogen - Nitrogen; Hydrogen - Oxygen; Hydrogen - Fluorine.
Hydrogen bonds characteristics
Hydrogen bonds are the strongest intermolecular force, leading to higher melting and boiling points.
Explain how intermolecular forces of attraction affect a molecule’s physical properties
The stronger the intermolecular force of attraction, the higher the melting and boiling point.
Explain why ammonia and water have high boiling points
Ammonia and water have high boiling points due to hydrogen bonding.
Explain how to predict the solubility of a compound
Consider whether there is hydrogen bonding and the spatial arrangement of polar covalent bonds.
What is reduction?
Reduction is the gain of electrons by a reactant.
What is oxidation?
Oxidation is the loss of electrons by a reactant.
State the definition of a redox reaction
A Redox Reaction is when an oxidation and a reduction reaction takes place at the same time.
What is an oxidising agent?
Oxidising agent is a substance that accepts electrons.
What is a reducing agent?
Reducing agent is a substance that donates electrons.
What can elements with low electronegativities do?
Elements with low electronegativities can form ions by losing electrons.
Where are oxidising agents on the electrochemical series
Oxidising agents are at the bottom left side of the electrochemical series.
Where are reducing agents on the electrochemical series?
Reducing agents are at the top right column of the electrochemical series.
What can oxidising agents be used for?
Oxidising agents can be used to kill fungi and bacteria and as a bleach.
Balance ion equations stages
- Balance the ions; 2. Balance the oxygen by adding water; 3. Balance the hydrogen by adding hydrogen ions; 4. Balance the change.
Combine ion-electron equations to produce redox equations stage 1
Before combining the equations, the number of electrons must be equal in each equation.
Combine ion-electron equations to produce redox equations stage 2
Combine equations.
Combine ion-electron equations to produce redox equations stage 3
Cancel out electrons and anything else that appears on both sides.
how to find the least ionic character
least ionic means the smallest electronegativity difference
how to find if an Atom is larger than an ion
compare the number of occupied electron shells
what elements don’t contain LDFs
covalent network
what elements tend to be reduced
elements with high electronegativities tend to be reduced
which atom has the greatest attraction for bonding electrons
the atom which is the most electronegative
