Chapter 2 Notes
Learning Goals
1. Use atomic symbols to represent isotopes and ions
2. Familiarity with the organization of the periodic table
3. Determine and use molar mass/average mass
2.5- Structure of the atom
1808-Dalton’s Theory: first theory of elements being composed of atoms; all atoms of a
singular element are the same; when there is a reaction, particles have changed
~1890-electrons are discovered
~1895-radioactivity is proposed
~1900-atoms contain electrons but had no charge
Different models of atoms: Thompson’s plum pudding model
Rutherford’s model
Bohr’s model (“typical idea” of an atom, most common)
● Rutherford fired particles at hyper-thin sheets of metal and most passed through,
leading him to believe there must be some empty space to an atom
● Bohr model: a nucleus with electrons orbiting, empty space in the middle
1 amu=1/12 the mass of C-12 (Carbon 12) atom which contains 6 protons and 6
neutrons
● Electrons are really disregarded when finding the mass of an element on the
atomic level
● Protons are what makes an element unique, you cannot change the number of
protons, that changes which element you have
● You can change the number of electrons, to a point
● Isotopes can vary in the number of neutrons, but they still have the same atomic
number [subtract the mass from the atomic number for the number of neutrons]
● Ions have more/less electrons depending on the environment that they are in and
give off an electric charge
● Positive = cations
● Negative = anions
● Metals tend to lose electrons, becoming cations
● Nonmetals tend to gain electrons, becoming anions
Intensive-independent of sample size
Learning Goals
1. Use atomic symbols to represent isotopes and ions
2. Familiarity with the organization of the periodic table
3. Determine and use molar mass/average mass
2.5- Structure of the atom
1808-Dalton’s Theory: first theory of elements being composed of atoms; all atoms of a
singular element are the same; when there is a reaction, particles have changed
~1890-electrons are discovered
~1895-radioactivity is proposed
~1900-atoms contain electrons but had no charge
Different models of atoms: Thompson’s plum pudding model
Rutherford’s model
Bohr’s model (“typical idea” of an atom, most common)
● Rutherford fired particles at hyper-thin sheets of metal and most passed through,
leading him to believe there must be some empty space to an atom
● Bohr model: a nucleus with electrons orbiting, empty space in the middle
1 amu=1/12 the mass of C-12 (Carbon 12) atom which contains 6 protons and 6
neutrons
● Electrons are really disregarded when finding the mass of an element on the
atomic level
● Protons are what makes an element unique, you cannot change the number of
protons, that changes which element you have
● You can change the number of electrons, to a point
● Isotopes can vary in the number of neutrons, but they still have the same atomic
number [subtract the mass from the atomic number for the number of neutrons]
● Ions have more/less electrons depending on the environment that they are in and
give off an electric charge
● Positive = cations
● Negative = anions
● Metals tend to lose electrons, becoming cations
● Nonmetals tend to gain electrons, becoming anions
Intensive-independent of sample size
