What are atoms made of? ▪ Know the three subatomic particles and

their relative charges and masses – Table 2.1

▪ Know that a neutron is modeled as an electron + a proton

▪ Define amu, why it exists and the conversion between amu and grams

▪ Distinguish between mass number and atomic number

▪ Know how to write the mass and atomic numbers in a formula

• All matter is composed of very tiny particles, which Dalton called atomsatoms.

• A moleculemolecule is a tightly bound combination of two or more atoms that acts as a single unit.

10-15 m

Neutron

Proton

Nucleus (protons and neutrons)

Space occupied by electrons

10-10 m

Subatomicparticle

Mass(g)Charge

Location in an atom

Proton

Electron

Neutron

1.6726 x 10-24

9.1094 x 10-28

1.6749 x 10-24

1

0.0005

1

+1-1

0

In the nucleus

Outside the ucleus

In the nucleus

1.0073

1.00875.4859 x 10-4

Mass (amu)

Mass (amu);to one

significantfigure

1 amu = 1.6605 x 10-24 g

2.2 - Classifying Matter ▪ Define the terms element,

compound, mixture, pure substance, homogeneous and heterogeneous mixtures

▪ Learn the system for classifying matter

Element:Element: a substance (for example, carbon, hydrogen, and iron) that consists of identical atoms.

There are 116 known elements.Of these, 88 occur in nature; the others have been made by chemists and physicists.

• Monatomic elements:Monatomic elements: consist of single atoms; for example, helium (He) and neon (Ne).

• Diatomic elements:Diatomic elements: there are seven elements that occur as diatomic molecules:– H2, N2, O2, F2, Cl2, Br2, and I2

• Polyatomic elements:Polyatomic elements: some elements have three or more atoms per molecule:– O3, P4, S8

– diamond has millions of carbon atoms bonded together to form one gigantic cluster.

• Compound:Compound: a pure substance made up of two or more elements in a fixed ratio by mass.

• Formula of a compound:Formula of a compound: tells us the ratios of its constituent elements and identifies each element by its atomic symbol.– NaCl: the ratio of sodium atoms to chlorine atoms

in sodium chloride is 1:1

– H2O: the ratio of hydrogen atoms to oxygen atoms in water is 2:1

• Mixture:Mixture: a combination of two or more pure substances– The substances may be present in any mass ratio.– Each substance has a different set of physical

properties.– Mixtures may be homogeneous or heterogeneous.– If we know the physical properties of the individual

components of the mixture, we can use appropriate physical means to separate the mixture into its component parts.

Homo- or Heterogeneous mixture?Pure substance or compound?

2.3 – Atomic Theory ▪ Understand the Law of Conservation of Mass ▪ Know that an atom CANNOT be divided by an ordinary

chemical reaction.

• Law of Conservation of Mass– Matter can be neither created or destroyed.– As Dalton explained, if matter is made up of

indestructible atoms, then any chemical reaction just changes the attachments among atoms, but does not destroy the atoms themselves.

OPb PbO C OOC

Carbonmonoxide

Leadoxide

Carbon dioxide

Lead

+ +

OWL 2.3

2.4 – What are atoms made of? ▪ Define the word isotope and how it

relates to the number of neutrons of a particular type of atom

▪ Know the two conventions for writing isotopes

▪ Define atomic weight ▪ Define the atomic weight of the

average atom (what’s in the periodic table)

• Isotopes:Isotopes: atoms with the same number of protons but a different number of neutrons.– carbon-12 has 6 protons and 6 neutrons;– carbon-13 has 6 protons and 7 neutrons;– carbon-14 has 6 protons and 8 neutrons;

• Most elements found on Earth are mixtures of isotopes:– chlorine is 75.77% chlorine-35 (18 neutrons) and

24.23% chlorine-37 (20 neutrons).

C136C

136

C126C

126

C146C

146

• Mass number:Mass number: the number of protons and neutrons in the nucleus of an atom.– the mass of the electrons in an atom is so small

compared to that of its protons and neutrons that electrons are not counted in determining mass number.

• Atomic number:Atomic number: the number of protons in the nucleus of an atom.

• a carbon atom of this composition is referred to as carbon-12.

Mass number (number of protons & neutrons)Atomic number (number of protons)6

12C

• Atomic weight:Atomic weight: the weighted average of the masses (in amu) of the naturally occurring isotopes of an element.– example: chlorine is 75.77% chlorine-35 and

24.23% chlorine-37

75.77100

x 34.97 amu + 24.23100

x 36.97 amu = 35.45 amu

chlorine-35 chlorine-37 17Cl

35.4527

atomic weight in the Periodic Tableis given to four

four decimal places

2.5 - The Periodic Table ▪ Apply the words Group and Period ▪ Know the location of the metals, nonmetals, main group

elements, halogens, alkali metals, alkali earth metals, transition metals, inner transition metals, halogens, and noble gases

2.6 & 2.7 – The arrangement of “ground state” electrons in atoms ▪ Know the components of an electron configuration

o Principal energy level (“shell”) o Orbital - Orbital shapes and orientaions

▪ Relate electron configurations to the Periodic Table ▪ Know how to write an electron configurations ▪ Know how to write orbital “box” diagrams and how they

relate to orientations of orbitals

8A

1s7A6A5A4A3A

2B1B8B8B

1A

8B7B

2A

6B5B4B3B

1

2

3

4

5

6

7

1

2

3

4

5

6

7

6

7

Main group elements;s block (2 elements)

Transition elements;d block (10 elements)

Main group elements;p block (6 elements)

1s

Helium is also an s blockelement

3d

4d

5d

3p

4p

6d

2s

3s

4s

5s

6s

7s

2p

5p

6p

7p

4f

5f

Inner transition elements; f block

(14 elements)