Chemical element

A chemical element is a substance that cannot be changed into any other substance by a normal chemical reaction.

An element is made up of atoms containing electrons, protons and neutrons. Each atom in an element will contain the same number of protons and electrons, for example every carbon atom has six protons and six electrons.

The periodic table of the elements contains lists all of the elements in order of their number of protons and is laid out so that the elements in each group (vertical column) will have similar properties.

Just because two substances contain the same atoms does not always mean that they will have the same properties. Graphite and diamonds are both made completely from carbon atoms, but the way in which they join with each other means that the have different properties.

Atoms of the same element may also contain different numbers of neutrons. Atoms of the same element with different numbers of neutrons are called isotopes.

quiz
{A chemical element is a substance that ________ be changed into any other substance by a normal chemical reaction. + cannot - can - might - should
 * type="[]"}
 * Correct! A chemical element cannot be changed into any other substance by a normal chemical reaction.
 * Incorrect. A chemical element is a substance that remains unchanged in a normal chemical reaction.
 * Incorrect. The definition is definitive, not conditional.
 * Incorrect. The definition is not based on a recommendation.

{Each atom in an element will contain the same number of ________ and ________. + protons | electrons - electrons | neutrons - protons | neutrons - neutrons | electrons
 * type="[]"}
 * Correct! Each atom in an element has the same number of protons and electrons.
 * Incorrect. While atoms have electrons and neutrons, the defining characteristic of an element is the number of protons and electrons.
 * Incorrect. Neutrons can vary in isotopes of the same element.
 * Incorrect. The defining characteristic of an element is the number of protons and electrons.

{The periodic table of the elements lists all of the elements in order of their number of ________. + protons - electrons - neutrons - atoms
 * type="[]"}
 * Correct! The periodic table is organized based on the number of protons.
 * Incorrect. The periodic table is not organized based on the number of electrons.
 * Incorrect. The periodic table is not organized based on the number of neutrons.
 * Incorrect. The periodic table is organized based on elements, not individual atoms.

{Graphite and diamonds are both made completely from ________ atoms. + carbon - hydrogen - oxygen - nitrogen
 * type="[]"}
 * Correct! Both graphite and diamonds are forms of carbon.
 * Incorrect. Graphite and diamonds are not made of hydrogen atoms.
 * Incorrect. Graphite and diamonds are not made of oxygen atoms.
 * Incorrect. Graphite and diamonds are not made of nitrogen atoms.

{Atoms of the same element with different numbers of neutrons are called ________. + isotopes - ions - molecules - compounds
 * type="[]"}
 * Correct! Atoms of the same element with different numbers of neutrons are isotopes.
 * Incorrect. Ions are atoms or molecules with a net electric charge.
 * Incorrect. Molecules are made up of two or more atoms.
 * Incorrect. Compounds are made up of atoms of different elements.