Kinds of Atoms
There are 92 naturally occurring elements, each with a different number of
protons and a different arrangement of Dmitri Mendeleev arranged the known
elements in a table according to their atomic mass (figure 2.
8), he discovered found that the elements in the table exhibited a pattern of
chemical properties that repeated itself in groups of eight elements.
This periodically repeating pattern lent the table its name: the periodic table of
elements.
The Periodic Table The eight-element periodicity that Mendeleev found is based
on the interactions of the electrons in the outer energy levels of the different
elements.
called valence electrons and their interactions are the basis for the differing
chemical properties of the elements.
For most of the atoms important to life, an outer energy level can contain no
more than eight electrons; the chemical behavior of an element reflects how
many of the eight Elements possessing all eight electrons in their outer energy
level (two for helium) are In sharp contrast, elements with seven electrons (one
energy level, such as fluorine (F), chlorine (Cl), and extra electron needed to fill
the energy level.
Elements with only one electron in their outer energy level, such as very reactive;
they tend to lose the single electron in their outer level.
Mendeleev’s periodic table thus leads to a useful generalization, the octet rule
(Latin octo, “eight”) or rule of eight: atoms tend to establish completely full outer
energy levels.
from this simple rule, combined with the tendency of atoms to balance positive
and negative charges.
Of the 92 naturally occurring elements on earth, only 11 are These 11 elements
have atomic numbers less than 21 and, thus, have low atomic masses.
levels of various elements in the human body; their levels in For example, silicon,
aluminum, and iron constitute 39.
2% of the earth’s crust, but they exist in trace On the other hand, carbon atoms
make up 18.
5% of the human body but only 0.
03% of A group of atoms held together by energy in a stable association is called
a molecule.
When a molecule contains atoms of more than one element, it is called a
compound.
atoms in a molecule are joined by chemical bonds; these bonds can result when
atoms with opposite charges attract (ionic bonds), when two atoms share one or
more pairs of electrons (covalent bonds), or when atoms interact in other We will
start by examining ionic bonds, which form when atoms with opposite electrical
charges (ions) attract.
A Closer Look at Table Salt Common table salt, sodium chloride (NaCl), is a lattice
of ions in which the atoms are held together by ionic bonds Sodium has 11
electrons: 2 in the inner energy level, 8 in the next level, and 1 in the outer
(valence) level.
can be achieved if the valence electron is lost to another atom that also has an
unpaired electron.
There are 92 naturally occurring elements, each with a different number of
protons and a different arrangement of Dmitri Mendeleev arranged the known
elements in a table according to their atomic mass (figure 2.
8), he discovered found that the elements in the table exhibited a pattern of
chemical properties that repeated itself in groups of eight elements.
This periodically repeating pattern lent the table its name: the periodic table of
elements.
The Periodic Table The eight-element periodicity that Mendeleev found is based
on the interactions of the electrons in the outer energy levels of the different
elements.
called valence electrons and their interactions are the basis for the differing
chemical properties of the elements.
For most of the atoms important to life, an outer energy level can contain no
more than eight electrons; the chemical behavior of an element reflects how
many of the eight Elements possessing all eight electrons in their outer energy
level (two for helium) are In sharp contrast, elements with seven electrons (one
energy level, such as fluorine (F), chlorine (Cl), and extra electron needed to fill
the energy level.
Elements with only one electron in their outer energy level, such as very reactive;
they tend to lose the single electron in their outer level.
Mendeleev’s periodic table thus leads to a useful generalization, the octet rule
(Latin octo, “eight”) or rule of eight: atoms tend to establish completely full outer
energy levels.
from this simple rule, combined with the tendency of atoms to balance positive
and negative charges.
Of the 92 naturally occurring elements on earth, only 11 are These 11 elements
have atomic numbers less than 21 and, thus, have low atomic masses.
levels of various elements in the human body; their levels in For example, silicon,
aluminum, and iron constitute 39.
2% of the earth’s crust, but they exist in trace On the other hand, carbon atoms
make up 18.
5% of the human body but only 0.
03% of A group of atoms held together by energy in a stable association is called
a molecule.
When a molecule contains atoms of more than one element, it is called a
compound.
atoms in a molecule are joined by chemical bonds; these bonds can result when
atoms with opposite charges attract (ionic bonds), when two atoms share one or
more pairs of electrons (covalent bonds), or when atoms interact in other We will
start by examining ionic bonds, which form when atoms with opposite electrical
charges (ions) attract.
A Closer Look at Table Salt Common table salt, sodium chloride (NaCl), is a lattice
of ions in which the atoms are held together by ionic bonds Sodium has 11
electrons: 2 in the inner energy level, 8 in the next level, and 1 in the outer
(valence) level.
can be achieved if the valence electron is lost to another atom that also has an
unpaired electron.
