Chapter 6 Atomic Structure and Chemical Bonds
Section 1 Why do atoms combine?
A. The nucleus containing protons and neutrons, is at the center of an atom and is
surrounded by the electron cloud, an area of space around the nucleus where
electrons travel.
a. Electrons have a negative charge and do not travel in well-defined obits.
b. Each element has a different atomic structure consisting of a particular
number of protons, neutrons, and electrons.
B. The number and arrangement of electrons in the electron cloud determines the
physical and chemical properties of the element.
a. Electrons are arranged in different energy levels at different distances
from the nucleus.
b. The farther an energy level is from the nucleus, the more electrons it can
hold.
c. Electrons in the level closest to the nucleus have the lowest amount of
energy; electrons farthest from the nucleus have the highest amount of
energy.
C. Data from periodic table can be used to understand energy levels.
a. The atomic number is the same as the number of protons( or electrons ) in
an electrically neutral atom
b. The number of electrons in an element’s outermost energy level increases
from left to right across a period.
i. The first energy level is complete with two electrons, and the first
period has two elements.
ii. The last element in each of the other periods has eight electrons in
its outer energy level.
c. Each column in the periodic table contains one element family or group
with similar chemical properties
i. The noble gases in Group 8 do not combine easily with other
elements because their energy levels are stable.
ii. The halogens have 7 electrons in their outer energy levels;
reactivity of the halogens decreases down the group.
iii. The alkali metals in Group 1 have one electron in their outer
energy level; reactivity of the alkali metals increases down the
group.
D. An electron dot diagram is the symbol for the element surrounded by as many
dots as there are electrons in it outer energy level
a. Dots are written on four sides of the element symbol
i. One dot represents a single electron
ii. Paired electrons are represented by two dots
b. A chemical bond is the force that holds two atoms together
i. Electron dot diagrams can be used to show how atoms bond with
each other
ii. Atoms bond with other atoms so that each atom has a stable energy
level