Chapter #5: Glossary Terms

The smallest particle of an element that retains the identity of the element.

An electron is a negatively charged particle within the atom. An electron has a relative mass of 1, and they travle in regions of space around the nucleus, called energy levels.

-the number of electrons, especially in the last energy level of an atom, determines how many bonds an element has. 

-electrons are not confined to the nucleus so they can moe easily from one atom to another.

Symbol: e^- 

Subatomic particles are particles that make up an atom. These particles are the protons, neutrons and electrons.

The nucleus is the positively charged centre of an atom.

Protons are positively charged subatomic particles that have a relative mass of 1836. They are located inside the nucleus. The number of protons determines what atom it is. (ie. Hydrogen) 

A neutron has neutral particles. They have a relative mass of 1837 and are located inside the nucleus.

An energy level is a possible level of energy an electron can have in an atom. 

Atomic number is the number of protons in the nucleus of an atom, and the number of electronsin a neutral atom. 

Mass number is the sum of the number of protons and the number of neutrons in the nucleus of an atom.

Isotopes are atoms of an element that have the same number of protons but a different number of neutrons.

Each isotope has a unique mass numer so they speciy each isotope by placing it's mass number after the name of the element.

An isotop is written with the symbol of the element, dash, then the mass. Ex. O-15, O-16  

The Bohr-Rutherford diagrams are models of the atom in which a central positive nucleus is surronded by electrons in energy levels. 

They are used to show the arrangement of subatomic particles for an element.

• Protons and neutrons are placed in a centre circle (the nucleus)
• Electrons are placed surronding the nucleus in  energy levels.

• 1st energy level - 2 electrons
• 2nd energy level- 8 electrons
• 3rd energy level- 8 electons

Example:  Bohr-Rutherford diagram for calcium 

Atomis mass is the avergae mass of naturally occuring isotopes of an element. For example, the atomic mass of oxgen is 16. Atomic mass is the same as mass number. 

The periodic table is a system for organizing the elements into coloumns and rows, so that elements with similar properties are in the same coloumn (group).

Metal is typically an element that is hard, shiny, malleable and ductile, and is a good conductor of heat an electricity. For example iron, copper, and gold. 

Non-metals are typically elements that are not shiny, malleable, or ductile, and is a poor conductor of heat and electricity. For example, oxygen and carbon. 

A metalloid is an element that shares some properties with metals and some with non-metals. For example, boron and silicon.

A period is a horizontal row of elements in the periodic table. They are numbered from 1 to 7. 

Agroup is a horizontal coloumn of elements in the periodic table. They are number from 1 to 18.

Alkali metals have a low melting point, they are soft enough to be cut with a knife and they are highly reactive. They are usally stored away from water and oxygen and they are found in Group 1 in the perodic table.

Examples: Sodium, Hydrogen and Lithium. 

Alkaline earth metals are also highly reactive but less so than alkali metals. They will burn in air if heated. The produce birght and colourful flames and they are found in Group 2 in the perodic table.

Example: Calcium, Magenesium and Beryllium.

Halogens are highly reactive and extremely corrosive non-metals. The melting point increases as you move from the top down. They are found in Group 17 in the perodic table.

Examples: Flourine, Chlorine and Bromine.

Noble gases are non-metals that are all colourless, odourless gases at room temperature. Their non-reactivity is their main property. They are found in group 18 in the periodic table.

Examples: Argon, Neon and Helium.

Valence electrons are any electrons in the outermost occupied energy level of an atom.