Atoms, Ions, and Isotopes

1. Atoms, Ions, and Isotopes

2. Atoms, Ions, and Isotopes • All matter is composed of particles called atoms. • An atom is the smallest unit of an element that carries the general properties of that element. • Atoms are composed of subatomic particles. • The three most important subatomic particles are protons, neutrons, and electrons.

3. Atoms, Ions, and Isotopes • A proton is a subatomic particle that has a charge of +1. • A proton is a subatomic particle that has a mass of ≈1 amu(amu = atomic mass unit). • A proton can be symbolized two different ways! letter symbol: or the mass-charge symbol: (the superscript = mass & the subscript = charge). p 11H

4. Atoms, Ions, and Isotopes • A neutron is a subatomic particle that has a charge of 0 (zero). • A neutron is a subatomic particle that has a mass of ≈1 amu(In reality, a neutron is slightly more massive than a proton). • A neutron can be symbolized two different ways! letter symbol: or the mass-charge symbol: (the superscript = mass & the subscript = charge). n 10n

5. Atoms, Ions, and Isotopes • An electron is a subatomic particle that has a charge of -1. • An electron is a subatomic particle that has a mass of ≈0 amu(In reality, an electron does have a very very very very small mass). • An electron can be symbolized two different ways! letter symbol: or the mass-charge symbol: (the superscript = mass & the subscript = charge). e- 0-1e

6. Atoms, Ions, and Isotopes proton → electron → neutron. • The subatomic particles in order of increasing mass: Ex. (1) Complete the following chart. 1 amu +1 11H p 1 amu 0 n 10n 0-1e 0 amu -1 e-

7. Atoms, Ions, and Isotopes n p e- Ex. (2) Rank the subatomic particles from highest to lowest mass. ______ > ______ > ______ • An atom’s atomic number (symbolized by the letter “Z”) is equal to its number of protons. • An atom’s mass number (symbolized by the letter “A”) is equal to the sum of its number of protons and neutrons. • Caution: mass number is not the same as atomic mass, which will be explained later. mass number ≠ atomic mass

8. Atoms, Ions, and Isotopes • An ion is a charged atom or group of atoms. • An ion composed of a single atom is called a monoatomic ion. Na1+ Cu2+ Al3+ Cl1- O2- As3- • An ion composed of two or more atoms is called a polyatomic ion (see Reference Table E). NO31- NH41+ SO42- H3O1+ PO43-

9. Atoms, Ions, and Isotopes • A positively charged ion (one that has more protons than electrons) is called a cation. Na1+ Cu2+ Al3+ NH41+ H3O1+ • A negatively charged ion (one that has more electrons than protons) is called an anion. Cl1- O2- As3- NO31- SO42- PO43- • In a atom, the number of protons is equal to the number of electrons.

10. Atoms, Ions, and Isotopes • Dalton proposed, in his atomic theory, that atoms of the same element were exactly the same. • Isotopes of the same element exist because not all atoms of the same element are completely identical.

11. Atoms, Ions, and Isotopes • Isotopes can be defined in several ways that actually say the same thing. • Isotopes are two atoms of the same element that have different masses. • Isotopes are two atoms that have the same atomic number but that have different mass numbers. • Isotopes are two atoms that have the same number of protons but different numbers of neutrons.

12. Atoms, Ions, and Isotopes • Isotopes are identified by their isotope number which is the same as the mass number(the number of protons and neutrons)! Hydrogen-1has 1 proton and 0 neutrons. Hydrogen-2has 1 proton and 1 neutron. Carbon-12has 6 protons and 6 neutrons. Carbon-14has 6 protons and 8 neutrons.

13. Atoms, Ions, and Isotopes 20 19 Ex. (1) K-39: #p = _____ and # n = _____ Ex. (2) Ni-59: #p = _____ and # n = _____ Ex. (3) N-14: #p = _____ and # n = _____ Ex. (4) 56 p and 81 n : _____-_____ Ex. (5) 14 p and 15 n : _____-_____ Ex. (6) 43 p and 56 n : _____-_____ 28 31 7 7 Ba 137 Si 29 Tc 99