Transcript 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 H
1
(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: 10n
(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 very very very small mass).
• An electron can be symbolized two different ways!
letter symbol: eor
the mass-charge symbol:
0
-1e
(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
Charge
Symbol
Symbol
Mass
Proton
1 amu
+1
p
1 H
1
Neutron
1 amu
0
n
1
0n
Electron
0 amu
-1
e-
0
-1e
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.
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-
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.
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
Ex. (1) K-39: #p = _____
20
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