Elements and Compounds Flashcards
Atom
The smallest particle of an element
An atom is made up of even smaller “subatomic” particles.
Atomic Number
The number by which elements are ordered in the periodic table
Carbon has the atomic number 6 and is followed in the periodic table by nitrogen (7) and oxygen (8).
Boiling point
The temperature at which a substance changes from liquid to gas
The metal rhenium is the element with the highest known boiling point, 5590°C!
Brittle
Easily broken
Many non-metal elements are brittle, breaking easily when hit.
Chemical Bond
An attractive force that holds two atoms together
Chemical bonds are broken or formed during chemical reactions.
Chemical Formula
A symbol that shows the chemical composition of a substance
The chemical formula for water shows that it has 2 hydrogen atoms for each oxygen atom.
Chemcial Reaction
The re-arrangement of atoms to form one or more new substances
Hydrogen and oxygen gases chemically react to form a new substance, water.
Chemcial Symbol
One or two letters used to represent an element
The symbols for some elements come from Latin, such as Au for gold, from the Latin word ‘aurum’.
Compound
A substance made up of two or more types of atom bonded together
Water is a compound with molecules made of one oxygen atom bonded to two hydrogen atoms.
Element
A substance made up of only one type of atom
So far, 118 elements have been discovered. Gold is an element made up of only gold atoms.
Group
A column in the periodic table
Elements in the same group have similar properties. Atomic number increases from top to bottom.
Lattice
A repeating arrangement of atoms in a solid
Lattices are highly ordered structures held together by bonds between atoms
Malleable
Able to be hammered or pressed into shape without breaking
Most metals are malleable, allowing them to be hammered into thin sheets.
Melting Point
The temperature at which a substance changes from solid to liquid
In general, metals have higher melting points than non-metals.
Metal
A shiny element that conducts heat and electricity
Most elements are metals. They occupy the entire periodic table except the top right corner.
Mixture
A combination of substances that can be physically separated
The mixed substances are not chemically combined. Mud is a mixture of sand grains and water.
Molecule
A group of atoms bonded together
An oxygen gas molecule is made up of two oxygen atoms bonded together.
Noble Gas
An element that is highly non-reactive
Noble gases are located in the last group of the periodic table.
Non Metal
An element that typically does not conduct heat or electricity
Non-metals are located in the top right corner of the periodic table.
Non Reactive
Tending not to chemically interact with other substances
Helium is non-reactive. If you place a flame in helium gas, the flame will go out.
Period
A row in the periodic table
Elements in the same period have different properties. Atomic number increases from left to right.
Periodic Table
A grid arrangement of all known chemical elements
The modern periodic table was developed by Dmitri Mendeleev in the 1860s.
Pure substance
A single substance without anything mixed in
Elements and compounds are pure substances rather than mixtures.
Reactive
Tending to chemically interact with other substances
When reactive substances are mixed together, a chemical reaction occurs.
