Principles of Chemistry

State the relative mass and relative charge of an electron.

Describe where electrons are found within an atom.

An atom has atomic number 12. How many electrons does it have?

Write the electronic configuration of an atom with atomic number 12.

State the rule for filling electron shells up to the third shell.

Define the term isotope.

Chlorine has two naturally occurring isotopes: 35Cl (75% abundance) and 37Cl (25% abundance). Calculate the relative atomic mass (A_r) of chlorine. Show your working.

Draw a diagram to show the electronic configuration of a chlorine atom (atomic number 17), using shells and crosses (×) for electrons.

The diagram below shows the electronic configuration of atom X: First shell: 2 electrons Second shell: 8 electrons Third shell: 7 electrons State the number of electrons in each shell for atom X.

What is the total number of electrons in atom X?

Using your answer to part (b), state the group and period of atom X in the Periodic Table.

Two isotopes of atom X have mass numbers 35 and 37. Explain how these isotopes are similar and how they are different.

If a sample of atom X contains 75% of the isotope with mass number 35 and 25% of the isotope with mass number 37, which isotope is more abundant? Give a reason.

Isotopes of boron are shown by the symbols and . Explain how these two isotopes are alike and how they are different. Refer to subatomic particles in your answer.

State the rule for filling electrons into the shells (energy levels) of atoms, up to the third shell.

Draw a dot-and-cross diagram to show the electronic configuration of a nitrogen atom (atomic number = 7). Show electrons in shells and label each shell.

The atomic number of magnesium is 12. State the number of electrons in a neutral atom of magnesium and explain your answer.

Potassium (K) is found in Period 4, Group 1 of the Periodic Table. Deduce the electronic configuration for a potassium atom. Explain your reasoning.

Explain how the electronic configuration you wrote for potassium determines its position in the Periodic Table.

Nickel (Ni) has atomic number 28 and mass number 59. Calculate the number of protons, neutrons, and electrons in a neutral atom of nickel.

Using your answer to part (a) and the position of nickel in the Periodic Table, decide whether nickel is a metal or a non-metal. Explain your reasoning.

Tin (Sn) forms an oxide with the formula SnO2. Predict the acid-base character (acidic/basic/amphoteric) of this oxide and justify your answer based on tin's position in the Periodic Table.

Define the term 'atom' and give an example.

Explain why elements in the same group (excluding Group 0) of the Periodic Table show similar chemical properties.

Helium and neon do not form any compounds. Using atomic structure, explain why the Group 0 elements are inert.