The Atom
MATTER
Everything around us is
made of matter. If it
takes up space and has
volume, it is matter.
TREE
MATTER
WATER
NOT MATTER
ENERGY EMOTIONS
AIR
IDEAS
ATOMS
▪ Matter is composed of incredibly small atoms.
▪ Atoms are the basic building blocks of all matter.
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The Atom
STRUCTURE OF ATOMS
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The Atom
LANGUAGE OF ATOMS
PROTON (P)
NEUTRON (N)
ELECTRON (E)
▪ + charge
▪ Mass = 1 amu
▪ Location: In nucleus
▪ # Protons = # Electrons
▪ NO charge
▪ Mass = 1 amu
▪ Location: In nucleus
▪ - charge
▪ Mass = 0 amu
▪ Location: In electron cloud
▪ # Protons = # Electrons
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The Atom
LANGUAGE OF ATOMS
ATOMIC NUMBER is the number of protons (P) in an atom.
▪ The number of protons (atomic number) determines
the identity of an atom.
ATOMIC MASS is the number of protons (P) plus neutrons
(N) in the nucleus.
In summary, P = E
N = Atomic mass – P
E=P
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The Atom
LANGUAGE OF ATOMS
VALENCE ELECTRONS: the number of electrons in the
outermost energy level of the electron cloud
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The Atom
LANGUAGE OF ATOMS
VALENCE ELECTRONS determine the chemical
properties of atoms, including the reactivity of the atom.
▪ CHEMICAL PROPERTIES: Atoms with the same
number of valence electrons will have similar
chemical properties.
▪ REACTIVITY: The reactivity of an atom is its capacity
to undergo a chemical reaction with another atom.
The capacity to react is dependent on its valence
electrons.
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The Atom
GROUPS AND VALENCE ELECTRONS
SIMILAR PROPERTIES
● GROUPS are made of atoms having the SAME NUMBER OF
VALENCE ELECTRONS.
● Elements in a group have similar properties because they have the
same number of valence electrons.
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The Atom
REACTIVITY
● The atoms that react most easily with other atoms have
either the lowest number of valence electrons or the
highest number of valence electrons.
● Atoms with the lowest number of valence electrons are
highly reactive because they seek stability by releasing
their valence electron(s) to other atoms.
● Atoms with the highest number of valence electrons
are highly reactive because they seek stability by gaining
electrons to fill their outermost shell.
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