Essay on chemistry unit one definitions

Submitted By ploymanee
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Chemistry definitions

Acid: An acid is a proton (H+) donor
Base: A base is a proton acceptor
Alkali: An alkali is a soluble base that releases OH- ions in an aqueous solution
Salt: When the H+ ion of an acid is replaced by a metal ion or an NH4+
Mole: Amount of substance that has the same number of particles, as there are atoms in 12g of carbon-12
Empirical formula: The simplest whole number ratio of atoms of each element present in a compound
Molecular formula: The actual number of any type of atoms of each element in a molecule
Oxidation agent: A reagent that oxidises (takes electrons) from another species
Reduction agent: A reagent that reduces (adds electrons) from another species
Atomic radius: The distance from the nucleus and the outer shell

Isotopes: Isotopes are atoms of the same element with different number of neutrons and different masses
Relative atomic mass: The average mass of an atom (of an element) compared with 1/12th the mass of a carbon-12 atom
Relative isotopic mass: The mass of the isotope compared to 1/12th the mass of a carbon-12 atom
First ionisation energy: the energy required to remove the first electron from each atom in one mole of atoms in a gaseous state. x(g) > x+ (g) + e-
Second ionisation energy: The energy required to remove the second electron from each ion in one mole of 1+ ions in a gaseous state. x+(g) > x2+ (g) + e-
Orbitals: Orbitals are a region of space that can hold up to two electrons with opposite spins
Metallic bonding: The attraction between positive ions and delocalised electrons
Ionic bonding: Electrostatic attraction between oppositely charged ions
Covalent bonding: A shared pair of electrons
Dative covalent bond: A share pair of electrons with the bonded pair of electrons coming from the same atom
Electronegativity: The ability of an atom to attract electrons in a covalent bond
Polar molecules: Molecules containing polar bonds are not always polar

Exam answers

Thermal decomposition in group II
The ease of thermal decomposition decreases down the group
So more heat is needed
Reactivity down group II
As you go down the group, it gets more reactive
The number of shells increase
Shielding increases
The distance outweighs the increased nuclear charge
Therefore there is less attraction on the outermost shell
There is an increasing ease of forming a cation

Why does the ionisation energy decease down group II? / Explain the trend in atomic radius down group II / Explain melting and boiling points down group II
As you go down the group, there are more shells
Which means there is more shielding
The distance outweighs the increased nuclear charge
There is less attraction on the outmost electron
(There is a weaker attraction between the ions and delocalised electrons)

Why is Fluorine a P block element?
The highest energy sub-level being filled is the P sub level
1st ionisation energy trend
Electrons added to the same shell
Nuclear charge increases
Therefore there is a greater attraction on the outermost electron