Matter and Elements Chapter Quiz

Matter and Elements

• Matter is anything that occupies space and has mass.
• Elements are unique forms of matter with specific chemical and physical properties that can't be broken down into smaller substances by ordinary chemical reactions.
• There are 118 elements, but only 98 occur naturally.
• Each element is designated by a chemical symbol.
• The four elements common to all living organisms are: oxygen (O), carbon (C), hydrogen (H), and nitrogen (N).

The Structure of the Atom

• The smallest unit of matter retaining the element's chemical properties is the atom.
• An atom is composed of two regions: the nucleus, located at the atom's center, containing protons and neutrons; and the outermost region which holds electrons in orbit around the nucleus.
• Protons carry a positive charge, neutrons have no charge, and electrons carry a negative charge.
• Protons and neutrons are located in the nucleus of the atom, while electrons orbit around the nucleus in orbitals.
• The number of protons determines the element's atomic number.
• The number of neutrons is variable, leading to isotopes with different mass numbers.
• The mass number is the sum of the number of protons and neutrons.
• Atomic mass is the calculated mean of the mass numbers for naturally occurring isotopes.
• The masses of electrons are significantly smaller than protons or neutrons and are therefore ignored when calculating mass number.
• Electrons have negative charges equal to the positive charges of the protons in neutral atoms.
• The majority of the atom's volume is made up of empty space.