Atoms Ions and Isotopes Atoms Ions and Isotopes

Atoms, Ions, and Isotopes

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.

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: p or the mass-charge symbol: 1 1 H (the superscript = mass & the subscript = charge).

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: n or the mass-charge symbol: 10 n (the superscript = mass & the subscript = charge).

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 small mass). • An electron can be symbolized two different ways! letter symbol: eor the mass-charge symbol: 0 -1 e (the superscript = mass & the subscript = charge).

Atoms, Ions, and Isotopes • The subatomic particles in order of increasing mass: electron → proton → neutron. Ex. (1) Complete the following chart. Subatomic Particle Letter Mass Charge Symbol Mass Proton 1 amu +1 p 1 Neutron 1 amu 0 n 1 0 n Electron 0 amu -1 e- 0 -1 e 1 H

Atoms, Ions, and Isotopes Ex. (2) Rank the subatomic particles from highest to lowest mass. ______ > ______ n p > ______ e- • 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

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. Na 1+ Cu 2+ Al 3+ Cl 1 - O 2 - As 3 - • An ion composed of two or more atoms is called a polyatomic ion (see Reference Table E). NO 31 - NH 41+ SO 42 - H 3 O 1+ PO 43 -

Atoms, Ions, and Isotopes • A positively charged ion (one that has more protons than electrons) is called a cation. Na 1+ Cu 2+ Al 3+ NH 41+ H 3 O 1+ • A negatively charged ion (one that has more electrons than protons) is called an anion. Cl 1 - O 2 - As 3 - NO 31 - SO 42 - PO 43 - • In a atom, the number of protons is equal to the number of electrons.

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.

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.

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-1 has 1 proton and 0 neutrons. Hydrogen-2 has 1 proton and 1 neutron. Carbon-12 has 6 protons and 6 neutrons. Carbon-14 has 6 protons and 8 neutrons.

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