Atomic Structure

ATOMS All matter in the universe is composed of tiny particles These particles are called Atoms Atom Matter Tiny Particles

ATOMIC STRUTURE Atoms are composed of smaller parts called subatomic particles These particles are called protons, neutrons, and electrons are tightly bound in a tiny nucleus The nucleus is located in the center of an electron cloud The electron cloud is the space where electrons are moving freely in areas of space called energy levels. An Atom Protons and neutrons

Protons, Neutrons, Electrons Protons have a positive charge Neutrons have no charge. Electrons have a negative charge. Electrons are the smallest and lightest of the particles in an atom Protons and Neutrons are much larger and heavier than electrons Protons and Neutrons can be broken down further into Quarks

Summary

The Complete Picture Matter Is made up of Atoms Atoms have a Nucleus surrounded by a cloud of Electrons Protons and Neutrons are tightly bound in the tiny Nucleus Protons and Neutrons are made of Quarks

The Electron cloud The negative electrons are attracted to the positive nucleus an that is how they stay, moving around in the cloud. The protons and neutrons are stuck together in the nucleus of an atom. They do not move. The positive charge of the protons makes the nucleus positive.

Electrons exist in energy levels in the cloud

Practice Questions

DO NOW!!!

Unique Atoms Each element in the periodic table has it’s own unique type of atom. But…. How do we determine the Identity of an atom?

ATOMIC NUMBER The number of protons determines the identity of an atom (an element). All atoms of the same element have the same number of protons. This is called the ATOMIC NUMBER The atomic number of an element can be found on the periodic table. Since it is the same for all atoms of that element, it is always a whole number.

MASS NUMBER Only the total number of protons and neutrons within its nucleus determines the mass of the atom, because the mass of the atom’s electrons is insignificant by comparison. The mass number of a particular atom is the sum of that atom’s protons and neutrons. The mass number cannot be found on the periodic table. (The mass number is not the same as atomic mass and cannot be found by rounding off atomic mass.)

Atomic and Mass Number

Isotopes Atoms of the same element have the same number of protons but sometimes the number of neutrons they have vary. These atoms are called isotopes of an element. Ex Chlorine, Cl Isotopes will have different mass numbers but the same atomic number

Atomic Mass Atomic mass is different from mass number!!!!! The Atomic mass of an element as seen on the periodic table is the weighted average of the masses of the naturally occurring isotopes of an element. The atomic mass of an element can be found on the periodic table. Since it is an average, it is usually not a whole number.

Quick Activity!!! P 84

Number of electrons The number of electrons an atom has is equal to the number of protons it has. This is why atoms have no charge. An atom of a given element may lose or gain electrons yet it still remains the same element.

Practice Exercise Atomic # = # of Electrons = # of Protons Mass # = # of Protons + # of Neutrons ElementAtomic number Mass number Number of Neutrons Number of protons Number of electrons H Fe Ca44

Atomic # = # of Electrons = # of Protons Mass # = # of Protons + # of Neutrons ElementAtomic number Mass number Number of Neutrons Number of protons Number of electrons He K Ca21