CH. 2: Elements & Particles

What are elements?

Elements are special forms of matter that consist of unique individual chemical and physical properties. They cannot be broken down into smaller substances.

What are the four most common elements in life?

COHN:

1. Carbon

2. Oxygen

3. Hydrogen

4. Nitrogen

What are trace elements?

Trace elements are ones that are needed for survival, but in much smaller quantities than essential elements.

How many natural elements are there? How many of them are essential?

There are ~92 natural elements. Only about 20-25% of those elements are essential for survival.

Which number on the periodic table represents protons?

The number on the periodic table that represents protons is the atomic number.

What are the three subatomic particles?

Proton, electron, and neutron.

What two subatomic particles are used to calculate an atom’s atomic mass?

Neutrons + Protons = Atomic Mass

What is valence?

Valence is an atom’s bonding capacity, which is determined by the number of unpaired electrons.

How many regions does an atom have and what are they?

An atom has two regions, the nucleus and the electron cloud.

Describe the properties of electrons.

Electrons are the subatomic particles found in the electron cloud of an atom. Electrons lack a set position, and only hover around the atom due to an electrostatic attraction between the nucleus and the electron cloud. They possess a -1 charge and a negligible mass.

Describe the properties of protons.

Protons reside inside the nucleus and possess a +1 charge and have a mass of 1. They determine an atom’s chemical properties.

Describe the properties of neutrons.

Neutrons are present within the nucleus and possess a neutral charge, or 0, and they have a mass of 1.

What is the unit of measurement for atomic mass?

Daltons.

TRUE or FALSE: Atoms are rarely neutral in nature.

True.

What does it mean when an atom is neutrally charged?

An atom is neutrally charged when the number of protons in an atom is equal to the number of electrons.

What are covalent bonds?

Covalent bonds occur when there are two atoms that stand to gain an electron to complete their outer shell. Instead of yanking the electron away completely, the two atoms share it and fill their valence shells.

TRUE or FALSE: Only one pair of valence electrons can be shared.

False.

How many atoms need to bond to create a molecule?

Two or more.

What are the shells of an atom called?

The valence shells.

How many electrons can the innermost valence shell contain? How many can the outermost?

The innermost valence shell can only contain 2 electrons, the outermost can contain, and is at its most stable when it has, 8.

Atoms with fulfilled valence shells are:

Inert.