atoms, ions, and molecules

Atoms, Ions, and Molecules

Chapter 2 Section 1

Living things consist of atoms of different elements.

• ATOM – the smallest basic unit of matter

– What is matter?• Something that has mass and takes up space

• ELEMENT – a group of atoms of the same type

– Examples: Hydrogen, Oxygen, Carbon, Nitrogen, etc.

H

O

Parts of the Atom• Nucleus (location – center of the atom)

– Proton • Positive Charge (+)

– Neutron• Neutral Charge (0)

• Energy levels (location – surrounds nucleus)– Electrons

• Negative Charge (-)

Atomic # & Atomic Mass

• Atomic #– the # of protons (or electrons)

• Atomic Mass– the # of protons and # of neutrons

• # of Neutrons = Atomic Mass – Atomic #

Use the periodic table to complete the table shown below:

ELEMENT SYMBOL PROTON # NEUTRON # ELECTRON #

Gold

Helium

Titanium

Arsenic

Mercury

Carbon

Iridium

Scandium

Nitrogen

Sodium

Au 7979 1182 2He 2

Electron Energy Levels

• First Energy Level–Maximum of 2 electrons (e-)

• Second Energy Level–Maximum of 8 e-

• Third Energy level and beyond–Stable with 8 e- in outer shell

Oxygen atom (O)

Nucleus:8 protons (+)8 neutrons

outermost energy level: 6 electrons (-)

inner energy level: 2 electrons (-)

Bonding• Not all atoms have full outer shells

– They are not “happy” or “stable”– They form bonds with other

“unhappy” atoms to complete their outer shells

• Compound – a substance made of atoms of different elements– Examples: CO2, H20, NaCl, CH4

REVIEW

• How are elements different from compounds?

• How many electrons are needed to fill the outer energy level of oxygen?

Compounds are made of different elements

2

Ionic Bonding• An ion is an atom that has gained or lost

one or more electrons.– positive ions (lose electrons)– negative ions (gain electrons)

Ionic bonds form between oppositely charged ions.Example: NaCl

Covalent Bond• Covalent bonds form when atoms share one or

more pairs of electrons- produce strong bonds- examples: CO2, CH4, H2O

Molecule – two or more atoms held together by covalent bonds

- examples: N2, H2, O2, CO2, H2O

It’s show time….

• Work as a team to develop a skit demonstrating each type of bonding!

REVIEW• What happens to electrons in outer energy levels when two atoms

form a covalent bond?–

• What distinguishes one element from another?–

• Describe the formation of an ionic compound.–

• What is the difference between an ionic bond and a covalent bond?–

• How does a molecule differ form an atom?

REVIEW• What happens to electrons in outer energy levels when two atoms

form a covalent bond?– Pairs of outer energy level electrons are shared

• What distinguishes one element from another?– The number of protons in the nucleus

• Describe the formation of an ionic compound.– One atom loses an electron, the other one gains an electron. The oppositely

charged ions formed are attracted to each other.

• What is the difference between an ionic bond and a covalent bond?– Electron pairs are shared in covalent bonds. Ionic bonds form when

electrons are transferred and the oppositely charged ions attract.

• How does a molecule differ form an atom?– A molecule is made up of two or more atoms held together by covalent

bonds.

Exit ticket: Answer one of the questions below using complete sentences:

• What part of an atom do you think would be the most fun and why?

• Relationships—which type of bonding would you like to be involved in and why?

Investigate Van der Waal’s forces and the gecko!http://www.youtube.com/watch?v=OoYeIsSkafIhttp://www.youtube.com/watch?v=gzm7yD-JuyM http://www.youtube.com/watch?v=HTbrsx1zARs