Chemical Changes And Structure Flashcards
How are elements arranged on the periodic table
By increasing atomic number
What do elements in the same group have in common
They have the same number of outer electrons
How do elements in the same group differ
Going down a group elements have an extra electron shell
What is the trend in elements across a period on the periodic table
Elements add an outer electron across the periodic table, they also change from metal to non metal elements
4 types of bonding found in the first 20 elements
Metallic
Covalent molecular
Covalent network
Monatomic
Which of the First 20 elements are metallic
Lithium
beryllium
Sodium
Magnesium
Aluminium
Potassium
Calcium
Which of the first 20 elements are covalent molecular
H2
N2
O2
F2
CO2
P4
S8
Carbon in the form of fullerene C60
Which of the first 20 elements are covalent networks X3
Boron
Silicon
Carbon (diamond, graphite)
Which of the first 20 elements are monatomic
Helium
Neon
Argon
What is meant by covalent radius
The measure of the size of an atom from the nucleus to outermost electron
Describe the trend in a covalent radius going down a group
Covalent radius increases as the number of occupied shells increase
Describe trend in covalent radius going along a period
Covalent radius decreases across the period as the nuclear charge increases
What is meant by the first ionisation energy
The energy required to remove one mole of electrons from one mole of gaseous atoms
What is meant by the second ionisation energy
The energy required to remove the second mole of electrons from one mole of gaseous atoms
What is meant by the second ionisation energy
The energy required to remove the second mole of electrons from one mole of gaseous atoms
Equation for the first ionisation energy of magnesium
Mg ——> Mg+ + e-
Equation for the second ionisation energy for calcium
Ca+ ——> Ca2+ + e-
Equation for third ionisation energy of aluminium
Al2+ ——> Al3+ + e-
Equation for third ionisation energy of aluminium
Al2+ ——> Al3+ + e-
What is meant by electro negativity
A measure of the attraction which an atom has for shared electrons in the bond
Describe the trend of electro negativity going down a group
Electro negativity decreases due to increase in shielding effect
Describe the trend of electro negativity across a period
Increases due to the increase in nuclear charge
How are covalent bonds formed
The result of two positive nuclei being held together by their common attraction for the shared pair of electrons
What is meant by polar covalent bonds
Form when atoms in a bind have different electro negativity values
What happens to the electrons in a polar covalent bond
The atom with a larger electro negativity value attracts the bonding electrons closer to it, this means that it has a delta negative charge and the other atom has a delta positive charge
What is meant by the term pure covalent
Pure covalent bonds are formed when the atoms in the bond have the same electro negativity value
Describe the bonding continuum
The bonding continuum shows the bonds by increasing ionic character
It goes from pure covalent bonds < polar covalent bind < ionic bond
Describe how the states of compounds at room temperature can help identify the type of bonding
- covalent networks are solid
- covalent molecular are gas or liquid
- ionic substances are solids
Describe how the melting points of compounds can help identify the type of bonding
Covalent molecular have low melting points, covalent networks and ionic substances have high melting points
Describe the solubility of different compounds
Solubility decreases as molecules increase in size. Polar covalent compounds and ionic compounds tend to be soluble in water and other polar solvents, nonpolar compounds are soluble and nonpolar solvents.
Describe the electrical conductivity of different compounds
Covalent molecular and covalent networks do not conduct electricity except graphite. Ionic bonds can conduct when molten or in a solution
What is meant by an intermolecular force
Act between molecules these are knows as van der waals forces
3 types on inter molecular force
London dispersion force
Permanent dipole permanent dipole
Hydrogen bonding
How do London dispersion forces arise
Formed by the electrostatic attraction between temporary dipoles and induced dipoles which are caused by the movement of electrons
Where are London dispersion forces found
Can operate between all atoms and molecules
Strength of LDFs
LDF is the weakest intermolecular force LDF gets stronger when there are more electrons as the strength of LDF increase the melting/boiling point increases
Explain when a molecule can be described as being polar
When they have permanent dipole - once end of the molecule is positive the other is negative caused by the atoms in the molecule having different electro negativities
Explain when a molecule can be described as being non polar
When the shape of the molecule is symmetrical
Describe a hydrogen bond
Formed between one molecule which contains hydrogen and another molecule which contained either nitrogen oxygen or fluorine
Strength of a hydrogen bond
Strongest intermolecular force
Explain how inter molecular forces of attraction affect a molecules physical properties
The higher the inter molecular force the higher the melting and boiling points the string the inter molecular force also increases viscosity
Why does ammonia and water have high melting points
They have hydrogen bonds between their molecules which increases the melting point
Explain how to fully predict the solubility of a compound
Like dissolves like, so polar compounds will dissolve in polar solvents and non polar compounds will dissolve in non polar solvents
What is meant by the term oxidation
The loss of electrons it can also mean the gain of oxygen or loss of hydrogen
What is meant by the term reduction
The gain of electrons it can also mean the loss of oxygen or gain of hydrogen
What is meant by a redox reaction
When oxidation and a reduction reaction take place at the same time
What is meant by the term reducing agent
A substance that donates electrons it is oxidised itself
What is meant by an oxidising agent
A substance that accept electrons it is reduced itself
Where are oxidising and reducing agents found in the periodic table
Strongest reducing agents are group 1
Strongest oxidising agents group 7
How to identify oxidising and reducing agents by their electronegativities
Elements with low electronegativities can form ions by losing electrons so act as reducing agents
Name some compounds that act as oxidising agents
Permanganate, dichromate and hydrogen peroxide
Uses of oxidising agents
Used to kill fungi bacteria and as a bleach
