The Building Blocks of Matter: Atoms Matter Anything that has mass and takes up space (volume)

The Building Blocks of Matter: Atoms

Matter

• Anything that has mass and takes up space (volume)

• Examples:
• A brick has mass and takes up space
• A desk has mass and takes up space
• A pencil has mass and takes up space
• Air has mass and takes up space

Atoms

• Smallest possible unit into which matter can be divided, while still maintaining its properties.

• Made up of:

• protons
• neutrons
• electrons

• The solar system is commonly used as an analogy to describe the structure of an atom

Atoms are so small that…

• it would take a stack of about 50,000 aluminum atoms to equal the thickness of a sheet of aluminum foil from your kitchen.

• if you could enlarge a penny until it was as wide as the US, each of its atoms would be only about 3 cm in diameter – about the size of a ping-pong ball

• a human hair is about 1 million carbon atoms wide.

• a typical human cell contains roughly 1 trillion atoms.

• a speck of dust might contain 3x1012 (3 trillion) atoms.

• it would take you around 500 years to count the number of atoms in a grain of salt.

Let’s Experiment

• In order to try to gain an idea of how small an atom really is, you will complete the following activity.

• Cut a strip of 11 in. paper in half.
• Discard one half.
• Cut the remaining piece in half.
• Continue cutting and discarding the strips as many times as you can.
• Make all cuts parallel to the first one. When the width gets longer than the length, you may cut off the excess, but that does not count as a cut.

Results

• How many cuts were you able to make?

• Do you think you could keep cutting the paper forever? Why or why not?

Protons (+)

• Positively charged particles

• Help make up the nucleus of the atom

• Help identify the atom (could be considered an atom’s DNA)

• Equal to the atomic number of the atom

• Contribute to the atomic mass

• Equal to the number of electrons

Neutrons

• Neutral particles; have no electric charge

• Help make up the nucleus of the atom

• Contribute to the atomic mass

Electrons (-)

• Negatively charged particles

• Found outside the nucleus of the atom, in the electron orbits/levels; each orbit/level can hold a maximum number of electrons ( 1st = 2, 2nd = 8, 3rd = 8 or 18, etc…)

• Move so rapidly around the nucleus that they create an electron cloud

• Mass is insignificant when compared to protons and neutrons

• Equal to the number of protons

• Involved in the formation of chemical bonds

Hydrogen (H) Atom

• Notice the one electron in the first orbital

Oxygen (O) Atom

• Notice the two electrons in the first orbital/level and the six in the second

Sodium (Na) Atom

• Notice the two electrons in the first orbital/level, eight in the second, and one in the third

The Atom’s “Center”

• Protons and neutrons are grouped together to form the “center” or nucleus of an atom.

QUARKS

• Particles that make up protons and neutrons

Sub-Atomic Particles Weight Comparison (protons, neutrons, electrons)

Sub-atomic Particles Size Comparison (protons, neutrons, electrons, & quarks)

Atomic Number

• The number of protons in the nucleus of an atom

Mass Number

• The total number of protons and neutrons in an atom’s nucleus

• Expressed in Atomic Mass Units (amu)

• Each proton or neutron has a mass of 1 amu

Building Atoms

• Using the whiteboard and the proton, neutron, and electron pieces, build the following atoms, and determine their atomic and mass numbers.

Atom Builder

• Using the interactive website link below, practice building atoms.

• http://www.pbs.org/wgbh/aso/tryit/atom/

FORCES IN THE ATOM

• Gravitational Force

• Electromagnetic Force

• Strong Force

• Weak Force

Gravitational Force

• The force of attraction of objects due to their masses

• The amount of gravity between objects depends on their masses and the distance between them

Electromagnetic Force

• The force that results from the repulsion of like charges and the attraction of opposites

• The force that holds the electrons around the nucleus

Strong Force

• The force that holds the atomic nucleus together

• The force that counteracts the electromagnetic force

Weak Force

• This force plays a key role in the possible change of sub-atomic particles.

• For example, a neutron can change into a proton(+) and an electron(-)

• The force responsible for radioactive decay.

• Radioactive decay  process in which the nucleus of a radioactive (unstable) atom releases nuclear radiation.

Isotopes

• Atoms that have the same number of protons, but have different numbers of neutrons

• Examples

Atomic Mass

• The weighted average of the masses of all the naturally occurring isotopes of an element

• The average considers the percent abundance of each isotope in nature

• Found on the periodic table of elements

• Example

Ion

• Charged particle that typically results from a loss or gain of electrons

• Two types:

• Anion = negatively charged particle
• Cation = positively charged particle

Building Ions

• Using the whiteboard and the proton, neutron, and electron pieces, build the following ions, and determine their atomic and mass numbers.