Special Sub-Topic: Basic Foundation Chemistry Click Here To Play: Basic Foundation Chemistry

What is an empirical formula?

The simplest ratio of atoms of each element in a compound. If a formula contains the actual numbers of the atoms, it is known as a molecular formula. For example, the molecular formula of ethane is C2H6, (it contains 2 carbons and 6 hydrogens) but its empirical formula is CH3. The mean mass of the atoms is the Ar, or relative atomic mass, and the sum of the particles in the nucleus is called the mass number.

To convert moles into grams, you use the equation: moles equals concentration times volume.

f. The formula used must have both the thing you start with and the thing you are trying to convert to. Therefore, the formula would be: moles equals mass divided by Mr (molecular mass).

During mass spectrometry, all of the following happen, but which order do they occur in?

Vaporisation, Ionisation, Acceleration, Deflection, Detection. Mass spectrometry is used to find the different isotopes of an element. The sample needs to be vaporised first, before being ionised by a heated filament. The sample is then accelerated into the flight tube and deflected by a magnetic field. (The heavier isotopes get deflected less). An ion detector then detects those present.

Ernest Rutherford discovered all of the following: electrons, neutrons, protons and the nucleus itself.

f. Rutherford put forward a model of the nucleus, but Geiger and Marsden (his research team) found it. Rutherford and Marsden discovered protons together. Rutherford theorised about neutrons, but James Chadwick discovered and named them. The discovery of electrons, however, did not involve Rutherford in any way - J J Thomson discovered those.

Atoms always have exactly the same number of electrons as they do protons in their nucleus.

t. Usually this is true. If the molecule had a charge, however, the number of electrons has changed (whereas the number of protons has remained the same). In this case the molecule is refered to as an ion, not an atom.

How many electrons can the f-subshell of an electron shell hold, when filled to its maximum?

14. The s-subshell can only hold two electrons, the p-subshell holds six electrons and the d-subshell holds ten electrons. As the number of subshells increases, so does the capacity of those subshells. (The f-subshell is next in line).

Who came up with the following? An atom in its ground state (lowest energy arangement) adopts a configuration with the greatest number of matching spins.

Hund. The Pauli Exclusion Principle is that no two electrons occupy the same orbital unless they have opposite spins.

What is the bond angle usually associated with a molecule of a trigonal planar shape?

120 degrees. 109.5 degrees is the bond angle of most tetrahedral shaped molecules (there is 109.5 degrees between each of the bonds). 107 degrees is the angle of a pyramidal shaped molecule (a triangular pyramid shape), and 180 degrees is the bond angle of a molecule with a linear shape.

The following is the definition of what? The ability of an atom to attract the bonding electrons.

Electronegativity. The molar mass is the mass of one mole of a substance. Malleability is a measure of how soft the substance is, and polarisation is when the electrons of an element are lined up.

Why is magnesium hydroxide used for indigestion remedies and toothpaste?

It is a weak alkali. Magnesium hydroxide is a weak alkali. This means it can neutralise the excess acid in the stomach, preventing indigestion. It can also neutralise the acids in the mouth which can cause tooth decay.