Q2WK3-IONS PDF Science 9 Week 3

IONS SCIENCE 9 WEEK 3  Atoms Atoms are the basic units of matter and the defining structure of elements. Structure of an Atom  PROTONS Protonis a subatomic particle with positive charge.  Neutrons Neutron is a subatomic particle with no charge. ...

IONS SCIENCE 9 WEEK 3  Atoms Atoms are the basic units of matter and the defining structure of elements. Structure of an Atom  PROTONS Protonis a subatomic particle with positive charge.  Neutrons Neutron is a subatomic particle with no charge.  Electrons Electron is a subatomic particle with negative charge.  NUMBER of PROTONS/ELECTRONS All atoms are electrically neutral. This implies that an atom must contain an equal number of protons and electrons so that the positive charges and the negative charges exactly cancel out.  NUMBER of PROTONS/ELECTRONS Atom of a neutral element has the same number of protons and electrons, it is also equivalent to its atomic number Condition (if atom is neutral) Element Atomic No. of No. of Number protons electrons Na 11 11 11 F 9 9 9  Condition (if atom has charge/ion) Element Atomic No. of No. of Number protons electrons Na+1 11 11 10 F-1 9 9 10  ATOMIC MASS The mass of the electrons in an atom can be ignored since electrons are so light that they have almost no mass. Therefore, the mass of an atom depends mainly on the number of protons and neutrons it has in its nucleus. The number of protons and neutrons in an atom is called atomic mass  ATOMIC MASS Atomic mass = no. of protons + no. of neutrons No. of neutrons = mass number – no. of protons or atomic number  ATOMIC MASS Element Atomic No. of No. of Atomic No. of Number protons electrons mass Neutron s Na 11 11 11 23 12 F 9 9 9 19 10  ATOMIC MASS Element Atomic No. of No. of Atomic No. of Number protons electrons mass Neutrons Na+1 11 11 10 23 12 F-1 9 9 10 19 10  LET’S TRY THIS Element Atomic No. of No. of Atomic No. of Number protons electrons mass Neutrons Ca 20 20 Al +3 10 27  LET’S TRY THIS Element Atomic No. of No. of Atomic No. of Number protons electrons mass Neutrons Zn 30 65 N -3 7 7  ION An ion is an atom or group of atoms that has a net positive or negative charge. The loss of one or more electrons from a neutral atom results in a cation, an ion with a net positive  ION For example, a sodium atom (Na) can readily lose an electron to become sodium cation. This is represented by Na+:  ION On the other hand, anion is an ion whose net charge is negative due to the increase in the number of electrons. A chlorine atom (Cl), for instance, can gain an electron to become the chloride ion Cl- : a. Which of the species are neutral? b. Which are negatively charged? c. Which are positively charged? d. What are the chemical symbols for all the species? The Sub-Atomic Particles