1
CHAPTER 1: ATOMIC STRUCTURE
(1.1) SUBATOMIC PARTICLES
● 3 subatomic particles:
1. Protons
2. Neutrons
3. Electrons
(1.1.1) PROTONS
● Protons → found in nucleus of an atom
● Each proton’s charge = same as the fundamental unit of charge = e = 1.6 x 10-19 C = “+1e” =
“+1”
● Each proton’s mass ≃ 1 atomic mass unit (amu)
● Atomic number (Z) (of an element) = the number of protons in an atom of that element
○ Acts as a unique identifier for each element/elements are defined by the number of
protons they contain
● NOT all atoms of a given element have the same mass (isotopes)
(1.1.2) NEUTRONS
● Neutrons → have no charge (A.K.A. neutral)
● Neutron mass = only slightly larger than proton mass
○ Protons + neutrons (in nucleus) make up almost entire mass of atom
● Mass number (A): sum of protons & neutrons in an atom’s nucleus
↳ Every atom has a characteristic mass number
● A given element can have a variable number of neutrons → atoms of the same element all
have the same atomic number, but not necessarily the same mass number
● Isotopes (of an element): atoms that share an atomic number but have different mass
numbers
● Symbol:
○ Z = atomic number
○ A = mass number
○ X = element symbol
(1.1.3) ELECTRONS
● Electrons → move through space surrounding nucleus & are associated with varying levels
of energy
, 2
● Electron charge = in magnitude to that of a proton, but negative = “-1e” = “-1”
● Mass of electron ≃ 1/2000th of a proton
● Electrostatic force of attraction between proton & electron charges far greater than
gravitational force of attraction (based on their respective masses)
● Electrons move around nucleus at varying distances → correspond to varying levels of
electrical potential energy
○ Electrons closer to nucleus are at lower energy levels / electrons that are further out
(A.K.A. in higher electron shells) have higher energy
● Valence electrons: electrons farthest from nucleus, which have the strongest interactions
with surrounding environment & the weakest interactions with nucleus
○ Much more likely to become involved in bonds with other atoms (because they
experience the least electrostatic pull from their own nucleus)
○ Generally determine the reactivity of an atom
○ Sharing or transferring of these in bonds allow elements to fill their highest energy
level to increase stability…
■ In neutral state → an atom has equal numbers of protons & electrons
■ Loss of electrons → atom has a (+) charge = cation: a positively charged atom
■ Gain of electrons → atom has a (-) charge = anion: a negatively charged atom
(TABLE 1.1) SUBATOMIC PARTICLES
● Proton →
○ SYMBOLS: p, p+,
○ RELATIVE MASS: 1
○ CHARGE: +1
○ LOCATION: nucleus
● Neutron →
○ SYMBOLS: n0,
○ RELATIVE MASS: 1
○ CHARGE: 0
○ LOCATION: nucleus
● Electron →
○ SYMBOLS: e-,
○ RELATIVE MASS: 0
○ CHARGE: -1
CHAPTER 1: ATOMIC STRUCTURE
(1.1) SUBATOMIC PARTICLES
● 3 subatomic particles:
1. Protons
2. Neutrons
3. Electrons
(1.1.1) PROTONS
● Protons → found in nucleus of an atom
● Each proton’s charge = same as the fundamental unit of charge = e = 1.6 x 10-19 C = “+1e” =
“+1”
● Each proton’s mass ≃ 1 atomic mass unit (amu)
● Atomic number (Z) (of an element) = the number of protons in an atom of that element
○ Acts as a unique identifier for each element/elements are defined by the number of
protons they contain
● NOT all atoms of a given element have the same mass (isotopes)
(1.1.2) NEUTRONS
● Neutrons → have no charge (A.K.A. neutral)
● Neutron mass = only slightly larger than proton mass
○ Protons + neutrons (in nucleus) make up almost entire mass of atom
● Mass number (A): sum of protons & neutrons in an atom’s nucleus
↳ Every atom has a characteristic mass number
● A given element can have a variable number of neutrons → atoms of the same element all
have the same atomic number, but not necessarily the same mass number
● Isotopes (of an element): atoms that share an atomic number but have different mass
numbers
● Symbol:
○ Z = atomic number
○ A = mass number
○ X = element symbol
(1.1.3) ELECTRONS
● Electrons → move through space surrounding nucleus & are associated with varying levels
of energy
, 2
● Electron charge = in magnitude to that of a proton, but negative = “-1e” = “-1”
● Mass of electron ≃ 1/2000th of a proton
● Electrostatic force of attraction between proton & electron charges far greater than
gravitational force of attraction (based on their respective masses)
● Electrons move around nucleus at varying distances → correspond to varying levels of
electrical potential energy
○ Electrons closer to nucleus are at lower energy levels / electrons that are further out
(A.K.A. in higher electron shells) have higher energy
● Valence electrons: electrons farthest from nucleus, which have the strongest interactions
with surrounding environment & the weakest interactions with nucleus
○ Much more likely to become involved in bonds with other atoms (because they
experience the least electrostatic pull from their own nucleus)
○ Generally determine the reactivity of an atom
○ Sharing or transferring of these in bonds allow elements to fill their highest energy
level to increase stability…
■ In neutral state → an atom has equal numbers of protons & electrons
■ Loss of electrons → atom has a (+) charge = cation: a positively charged atom
■ Gain of electrons → atom has a (-) charge = anion: a negatively charged atom
(TABLE 1.1) SUBATOMIC PARTICLES
● Proton →
○ SYMBOLS: p, p+,
○ RELATIVE MASS: 1
○ CHARGE: +1
○ LOCATION: nucleus
● Neutron →
○ SYMBOLS: n0,
○ RELATIVE MASS: 1
○ CHARGE: 0
○ LOCATION: nucleus
● Electron →
○ SYMBOLS: e-,
○ RELATIVE MASS: 0
○ CHARGE: -1
