Dot and cross diagrams are drawn for methane, CH4\mathrm{CH_{4}}CH4, ammonia, NH3\mathrm{NH_{3}}NH3, and water, H2O\mathrm{H_{2}O}H2O. Only the outer shell electrons are shown.
Statement 1: The central atom in each molecule has 8 electrons in its outer shell.
Statement 2: The numbers of non-bonding pairs on the central atom are 0 in CH4\mathrm{CH_{4}}CH4, 1 in NH3\mathrm{NH_{3}}NH3 and 2 in H2O\mathrm{H_{2}O}H2O.
Statement 3: Each hydrogen atom has 2 electrons in its shell.
Statement 4: A water molecule has more shared pairs of electrons than an ammonia molecule.
Which statements are correct?
1 and 3 only
1, 2 and 3 only
2 and 4 only
1, 2, 3 and 4
64 exam-style questions on OCR GCSE Chemistry 2.2 Bonding, covering 2.2.1 Metals, non-metals and the Periodic Table, 2.2.2 Types of chemical bonding and dot and cross diagrams, 2.2.3 Limitations of bonding models, and 2.2.4 Reactivity, atomic number and the modern Periodic Table. Each one has a worked solution and a mark scheme showing where the marks go.