10.1 – Structure of the Atom
- A chemical symbol is a shorthand way of writing the
name of an element.
- An atom consists of a nucleus made of protons and neutrons
surrounded by an electron cloud.
- Energy levels of electrons:
Level 1 – holds up to 2 electrons
Level 2 – holds up to 8 electrons
Level 3 – holds up to 18 electrons
Level 4 – holds up to 32 electrons
- The atomic number of an element is the number of protons
in the nucleus.
- The electrons in an atom are arranged in several energy
levels, each of which is able to hold a certain number of electrons.
- Know the elements represented by the following symbols:
AL, Ca, C, Cl, Cu, F, Au, He, H, I, Fe, Mg, Hg, N, O, K, Ag, Na
10.2 – Smaller Particles of Matter
- Quarks are particles of matter that make up protons
and neutrons.
- Protons can be broken into quarks by having them collide
while traveling near the speed of light.
10.3 – Masses of Atoms
- The mass number of an atom is the sum of the number
of protons and the number of neutrons.
- The number of neutrons in an atom can be computed by
subtracting the atomic number from the mass number.
- The isotopes of an element are atoms of that same element
that have different numbers of neutrons.
- The average atomic mass of an element is the average
mass of the mixture of its isotopes.
10.4 – The Periodic Table
- The periodic table of elements is an arrangement of
elements according to repeated changes in properties. It was devised
by Mendelov in the late 1800s.
- A dot diagram represents the electrons in the outer
energy level of an atom.
- In the periodic table, the 111 elements are arranged
in 18 vertical columns, or groups, and 7 horizontal rows, or periods.
- Metals are found at the left of the periodic table,
nonmetals at the right, and metalloids along the line that separates the
metals from the nonmetals.
- Most metals are solid at room temperature and are good
conductors of heat and electricity.
- Most nonmetals are gases at room temperature (though
some are brittle solids) and are poor conductors of heat and electricity.
- Metalloids have some properties of metals and some
properties of nonmetals.
- Elements in groups 3 through 12 are called transition
elements (such as copper and iron). They are metals, but have additional
properties. |
