When do atoms become ions

Allow time for discussions to come to agreed explanations. Support individual groups by using questions to focus their ideas. If a data projector is available, show an electronic animation of the formation of the sodium chloride ionic lattice. In a plenary:. Provide an opportunity for students to write down in what ways they have changed their original ideas, as a result of listening to others during the session.

Draw attention to ways in which individuals might need to develop their explanations further. The initial demonstration and discussion about the meaning of words such as atom, molecule and ion draw attention to the learning objectives. Students compare their responses to statements about the formation of ions and have the opportunity to articulate their ideas. The electronic animation showing the formation of a sodium chloride lattice helps students recognise the standard they are aiming for.

They examine how their ideas have developed during the session and written feedback supports students should they need to develop their understanding further. A procedure for demonstrating the reaction of chlorine and sodium when the metal is heated is available as the second part of a practical series on heating group 1 metals in air and in chlorine.

This resource includes a full kit list and safety instructions for heating sodium, lithium and potassium in air and in chlorine — only the steps required for heating sodium in chlorine are needed for this lesson plan.

Intructions for using silver nitrate solution to test for chloride ions are available as part of another resource on testing for negative ions. This lesson plan was originally part of the Assessment for Learning website, published in Assessment for Learning is an effective way of actively involving students in their learning.

Each session plan comes with suggestions about how to organise activities and worksheets that may be used with students. However, if the total number of electrons does not equal the number of protons, the atom has a net electrical charge. Any atom or molecule with a net charge, either positive or negative, is known as an ion. An ion consisting of a single atom is a monoatomic ion; an ion consisting of two or more atoms is referred to as a polyatomic ion. The positive electric charge of a proton is equal in magnitude to the negative charge of an electron; therefore, the net electric charge of an ion is equal to its number of protons minus its number of electrons.

Ions are highly reactive species. They are generally found in a gaseous state and do not occur in abundance on Earth. Ions in the liquid or solid state are produced when salts interact with their solvents. They are repelled by like electric charges and are attracted to opposite charges.

There are specialized types of ions. The outer shells of non-metal atoms gain electrons when they form ions:. For elements in groups 6 and 7, the charge on the ion is equal to 8 minus group number. Sulfur is in group 6 of the periodic table. What is the charge on its ions, and is the charge positive or negative?

A neutral sodium atom, for example, contains 11 protons and 11 electrons. Atoms that gain extra electrons become negatively charged.