Unit 1 Revision Chapter 2 - 8

Chapter 2 – A particle view of matter What you should be able to do: Describe the structure of the atom in terms of the arrangement of protons, neutrons and electrons Isotopes Calculate abundance and Relative Atomic Mass Electron configuration Excited and ground state

Atomic Theory Explains the structure of atoms Atoms are made up from sub-atomic particles. Protons – found in the nucleus and have a positive charge. Relative mass of 1 Neutrons – found in the nucleus and have no charge. Relative mass of 1 Electrons – orbit the nucleus in specific energy levels known as shells – take up most of the space occupied by an atom. Relative mass of 0.0005

Structure of the atom Protons:- Found in nucleus Neutrons:- Positive charge (+ve) Mass = 1 Number of protons is known as the Atomic number. Each element has a different number of protons. Protons are made form quarks and gluons. Neutrons:- Found in nucleus No charge Mass = 1 Neutrons act to stabilise the nucleus and hold the protons together with the strong force. The Relative atomic mass is the number of protons + number of neutrons. Neutrons are made form quarks and gluons. Electrons:- Found in (orbits) shells around the nucleus. Each shell and sub-shell represent a particular energy level that the electrons are found at. These energy levels can be explained by quantum mechanics. The number of electrons equals the number of protons unless the atom forms an ion.

Isotopes Most elements form isotopes An Isotope is an element that has atoms that have a different number of neutrons. The RAM on the periodic table is an average for that element taking into account the abundance of the isotopes for that element. Isotope calculations are an important part of chemistry. Page 38 of your text gives you the formula and an example of these types of calculations. A mass spectrometer can be used to detect the presence and number of isotopes present in a sample of an element. Mass Spectrometer Mass spectrum of Bromine molecules

Shells and Sub Shells

Chapter 3 – The periodic table What you should be able to do: Explain the periodic variation of elements Locate an element on the periodic table given electron configuration

Chapter 4 – Relative Atomic Mass and the Mole What you should be able to do: Calculate Relative Atomic Mass from isotopes and mass spectrometers n=m/M N=n x NA Calculate % by mass Determine empirical formula Determine molecular mass

Mole calculations n = m M Number of mol = mass of chemical in grams divided by its Molar Mass. m = n x M Mass of a chemical in grams = number of mol x Molar mass. M = m n Molar Mass of unknown chemical = mass in grams ÷ number of mole Particles = n x NA Particles present = number of mole x Avogadro's number. n = Particles NA Number of mole = Particles present ÷ Avogadro’s Number.

Percentage composition Percentage composition tells us the amount by mass of each element present in a compound. Molar mass = (39.1 x 2) + (52 x 2) + (16 x 7) = 294.2 gmol-1 % Oxygen = (16 x 7) x 100 294.2 1 = 38%

Empirical formula The simplest whole number ratio of atoms present in a compound. H2O C2H3O4 C6H12O6 You must be able to perform calculations to determine empirical formula.

Molecular formula The molecular formula is the actual formula of a chemical which is not always in its simplest form (empirical formula) To calculate the Molecular Formula: Molecular formula mass / empirical formula mass = the number of times the empirical formula

Practice Exam Questions Which of the following atoms is in its ground state? 1s22s23s2 1s22s22p5 1s22s22p63s24s1 1s22s22p63s23p63d54s2

Practice Exam Questions The element that can be found in group 2 period 4 of the Periodic Table is: Mg Ca Sr Ba

Practice Exam Questions The percentage by mass of uranium in uranium oxide (U3O8) is: 84.8% 82.3% 80.1% 88.5%

Practice Exam Questions The mass of 0.25 mol of aluminium oxide (Al2O3) is: 20.45g 25.23g 25.50g 22.19g

Practice Exam Questions The empirical formula of the compound with the composition: 42.9% carbon and 57.1% oxygen is: CO2 C2O2 CO C2O

Practice Exam Questions Which of the following atoms has the greatest number of neutrons? 57Co 58Fe 56Mn 56Ni

Practice Exam Questions Isotopes are Atoms that have the same atomic number but different numbers of electrons. Atoms that have different numbers of protons but have the same mass number. Atoms that have both the same number of protons and neutrons. Atoms that have the same number of protons but different mass numbers.

Practice Exam Questions Which of the following is not an empirical formula? C2H6 CH3COOH H2SO4 KCl

Practice Exam Questions The number of atoms present in 0.625 mol of H2O molecules is: 6.25 x 1021 6.25 x 1022 6.25 x 1023 6.25 x 1024

Practice Exam Questions The ground state electronic configuration, in terms of subshells, for the chloride ion is: 1s22s22p63s23p6 1s22s22p63s23p5 1s22s22p63s23p63d1 1s22s22p63s23p53d1

Practice Exam Questions The electronegativity values of elements in the periodic table have been found to follow certain trends. The correct statement concerning electronegativity values is that they: Increase from left to right across the periodic table and increase as you go down the table. Increase from left to right across the periodic table and decrease as you go down the table. Decrease from left to right across the periodic table and decrease as you go down the table. Decrease from left to right across the periodic table and increase as you go down the table.

Practice Exam Questions The ground state electronic configuration, in terms of shells, for the chloride ion is, 2, 8, 8. 2, 8, 7. 2, 8, 6. 2, 8, 7, 1.

Practice Exam Questions

Practice Exam Questions

Practice Exam Questions

Practice Exam Questions

Practice Exam Questions