Physical Science Chapter 4. Atoms The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged.

Physical Science

Chapter 4

Atoms• The atom is a basic unit of

matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons

Atoms

Atoms

• http://www.youtube.com/watch?v=FxDpZ8wGgZ8

• History of the atomic theory

What is an Atom

• http://www.youtube.com/watch?v=cnXV7Ph3WPk

Parts of the Atom

• The parts of the atom are called subatomic particles•Protons, electrons, and

neutrons are subatomic particles

Protons

• Positively charged particles found in the nucleus• Each proton has a charge of 1+• Some nuclei have more than

100 protons

Protons

Bellwork 9-30

•Discuss a scientific observation you made this weekend,• Then…draw an atom with

all of its subatomic particles from memory

Electrons

•Negatively charged particles found in the space outside the nucleus• Each electron has a charge

of -1

Electrons

Neutrons

•A neutral particle found in the nucleus of an atom• Its mass is almost exactly

equal to a proton

Neutrons

Properties of particles

•Protons, electrons, and neutrons can be distinguished by mass, charge, and location in an atom

Mass

• Protons and neutrons have almost the same mass• Takes almost 2000 electrons to

equal the mass of one proton• Electron’s charge, however, is

equal to that of the proton

Periodic table

Atomic Mass and Number

• http://periodictable.com/

Atomic Number

•Atomic number of an element equals the number of protons in an atom of that element

Atomic Number

• Atoms are neutral because they have the same number of electrons and protons• Therefore…• The atomic number also

equals the amount of electrons and atom has

Mass Number

• Atomic number gives the number of protons, nut not the # of neutrons•Mass number is the sum of the

protons and neutrons

•Atom of aluminum has 13 protons and 14 neutrons, what is its mass number?

Isotopes

• Dalton thought that all atoms of a given element were identical• Every atom of a given element

does have the same amount of protons and electrons,

Isotopes• But every atom of a given

element does not have the same number of neutrons• Isotopes are atoms of the

same element that have different numbers of neutrons and different mass numbers

Isotopes

• Look at figure 12 on page 112•What are some effects of

water water that contains hydrogen isotopes?

With a group of 2-3

• 1. How are the compositions of heavy water and ordinary water similar?

• What type of hydrogen atoms does ordinary water contain?

• What type of hydrogen atoms does heavy water contain?

• Compare the properties of heavy water and ordinary water.

When complete…

• Complete section one and 2 in your workbook•What you do not finish in class

will be homework

Bellwork

•How many neutrons are in an atom with an atomic number of 32 and an atomic mass of 68?

Atom

• http://www.youtube.com/watch?v=yqLlgIaz1L0

• http://www.youtube.com/watch?v=pV822HfqT44

Bohr

• Bohr’s model of the atom focused on the electron which is what makes his model the modern model

Energy Levels

• Electrons move with constant speed in fixed orbits around the nucleus• Each electron has a specific amount

of energy• Sometimes atoms gain or lose energy

and the energy in an electron can change

Energy Levels

• Energy levels: The possible energies that an electron can have.• The electrons in an atom can

move from one energy level to another when they gain or lose energy

• http://www.youtube.com/watch?v=VRTdaYbiSS4

How do we know?

• Scientists can measure the energy gained when electrons absorb energy and move to a higher energy level• They can also measure the energy

released when an electron moves to a lower energy level

How do we know?

• Some elements emit light when they release energy• Explosions can cause heat which

pushes electrons to higher energy levels

Electron cloud

• The electron cloud model is used to describe the possible locations of electrons around the nucleus.

Atomic Orbitals

• Orbital is the region of space around the nucleus where the electron is likely to be