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Atomic Structure. Elements. All elements are composed of only one type of atom. In these atoms are three subatomic particles: Protons Neutrons Electrons. Elements. -Protons have a positive charge (+) -Neutrons have no charge (neutral) -Electrons Have a negative charge (-).
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Elements All elements are composed of only one type of atom. In these atoms are three subatomic particles: Protons Neutrons Electrons
Elements -Protons have a positive charge (+) -Neutrons have no charge (neutral) -Electrons Have a negative charge (-)
Most of the mass of an atom is found in the nucleus which contains the neutrons and protons.
Atomic number • Atomic number tells you how many protons that elements has. • If the number of protons changes, the element changes.
Atomic number • Since the atom of an element is neutral, then the atomic number also tells you how many electrons you have. Atomic #=# of protons =# of electrons
Atomic Mass • Atomic mass is the total number of protons and neutrons found in the nucleus of an atom. • # of protons + #of neutrons = atomic mass
Neutrons • To find out how many neutrons and element has: • Round atomic mass to nearest whole number • Subtract atomic number from atomic mass to get number of neutrons Atomic Mass – Atomic Number = # of neutrons
Example • Na (sodium) • Atomic mass is 22.989 • Atomic mass rounded 23 • Atomic number is 11 Atomic Mass – Atomic Number = # of neutrons • 23-11= 12 • Na has 12 neutrons.
Try these!!! Co (Cobalt) Ag (Silver) Atomic massis 107.868 Atomic mass rounded 108 Atomic number 47 108-47 = 61. • Atomic mass is 58.933 • Atomic mass rounded 59 • Atomic number 27 • 59-27= 32
Bohr’s model • Is a physical drawing that shows where all the subatomic particles are located in a particular atom of an element. • The Bohr’s model is similar to our very own solar system.
Bohr’s Model • Protons and neutron are always found in the nucleus of the atom of an element. • Electrons are around the atom in an area called the electron cloud. • In this electron cloud are orbitals where electrons move around the nucleus of the atom.
Bohr’s Model • Each orbital can only hold a certain amount of electrons: • 1st orbital- 2 electrons • 2nd orbital- 8 electrons • 3rd orbital- 8 electrons • 4th orbital- 18 electrons
The elements found in a group have similar properties because they have the same number of valence electrons.
The horizontal rows on the periodic table are called a period. Periods tell you how many orbitals will be on your drawing. • Ex. Na (sodium) is in Period 3, it will have 3 orbitals in its Bohr’s Model.
The vertical columns on the periodic table are called groups. Groups tell you how many valence electrons the element has. • Ex. Na (sodium) is in Group 1 so it has 1 valence electron.
Valence electrons are the electrons that occupy the last orbital of an element. • Orbitals are also called energy levels.
Boron (B) 5 p+ 6 n
Al 13 p+ 14 n
Lewis-Dot Structure • The amount of dots you draw for a Lewis Structure (LS for short) is equal to the # of Valence Electrons in an Atom
Valence Electrons • The # of Valence e- an atom has is dictated by the Group that the Element is in • Groups are the Vertical Columns on the Periodic Table!!! It’s So Simple!!!!
Isotopes are atoms of a given element that have different numbers of neutrons and different mass numbers.
Ex. Oxygen-16; has 8 neutrons Oxygen-17; has 9 neutrons Oxygen-18; has 10 neutrons These are all still oxygen atoms.
Elements on the periodic table are classified as one of the following: • Metals • Nonmetals • Metalloids
