From Atoms to Materials

negative ion 負離子 anion 陰離子 Extension Language tip anion noun (pronunciation: an-ion ) 9 protons in nucleus 10 electrons fluorine atom fluoride ion gains 1 electron 9 protons in nucleus 9 electrons use the chemical symbol of the atom show the charge of the ion : +2 Ca 2+ use the chemical symbol of the atom show the charge of the ion : −1 F - Chemical symbols of ions An ion can be represented by a chemical symbol. For example, a calcium ion is represented by: Negative ions When an atom gains electron(s), there are more electrons in the atom than protons. The ion formed will carry a net negative charge . It is called a negative ion or an anion . For example, a fluorine atom has 9 protons and 9 electrons. Under certain conditions, it can gain one electron to form a fluoride ion. A fluoride ion is a negative ion (an anion); it carries one negative charge. Fig. 13.13 A fluorine atom (left) gains one electron to form a fluoride ion (right). Similarly, a fluoride ion is represented by: When atoms form ions, protons are never gained or lost. If the charge is +1 or −1, the number ‘1’ is left out. 26 © United Prime Educational Publishing (HK) Limited 2024 All rights reserved; no part of this publication may be reproduced, photocopied, recorded or otherwise, without the prior written permission of the Publisher. Sample