AtomsThe smallest particle of Matter

COS #1•I can use experiments to provide evidence that matter is made up of particles too small to be seen.

Experiment (E5)

• Follow experiment using cereal

Read E 6-7

• Explain how the atom model has changed from 1803 to 1926.• 1803 –English chemist, John Dalton’s model showed atoms as a solid

sphere of different sizes and masses.• 1897 – English scientist, JJ Thomas, discovered atoms contain

negatively charged particles (electrons). He thought the electrons were distributed evenly throughout the atom.• 1911 – New Zealand physicist, Earnest Rutherford, showed that atoms

have a small central core (nucleus) surrounded by empty space that electrons moved around in.

• 1913- Danish scientist, Niels Bohr, suggested the electrons travel in a specific orbit around the nucleus.• 1926 – Austrian scientist, Erwin Schrodinger, developed the electron

cloud model. “Clouds” or orbits represent the probability of finding an electron in a certain location.• 2, 8, 18, 32, 50• In a nutshell – the atom model went from a solid sphere to being

made up of 3 parts; electrons orbiting the nucleus (neutrons and protons).

• This is where the word atom comes from which is the smallest particle of an element.

Although atoms are extremely small, they are made of even smaller parts: nucleus, protons, neutrons and electrons.

Nucleus= the tiny, central core of the atom, which contains protons and neutrons.

Protons=have a positive electric charge (+).Neutrons=have no charge. (they are neutral)Electrons= very energetic particles that move in the space

around the nucleus and carry a negative charge (-).

In 1802, John Dalton (a British school teacher) proposed an atomic theory.

His main conclusions were:1. Atoms can’t be broken into smaller pieces.2. In any element, all of the atoms are exactly alike.3. Atoms of different elements are different.4. Atoms of two or more elements can combine to form compounds.5. Atoms of each compound have a unique mass.6. The masses of the elements in a compound are always in a constant

ratio. Today, scientists have identified some important exceptions to Dalton’s statements but his ideas still form the basis of our understanding of atoms.

Read E8: Draw and label the carbon atom in your notebook.

All atoms of a particular element have the same number of protons. Because the number of protons is unique to each element, this number is called the element’s atomic number.

Example: the atoms that make up the element carbon all have 6 protons so the atomic number for carbon is 6.

• Scientists can’t study atoms by looking at them. (They are too small to see!)

• So….How do they study them?

They make inferences about them based on observations.

They use models to make and test their predictions.

Vocabulary in notebook

WORD BANK (E5-13)Atom electron neutron proton

nucleus molecule element

The smallest particle of an element that still has the properties of the

element______________________________

Negatively charges particles that surround the nucleus of an atom

____________________________________

A substance that cannot be broken into another substance

___________________________

2 or more atoms joined together by certain forces of attraction called chemical bonds

_______________________________

A particle with no charge; in the nucleus of an atom

____________________________

A particle with a positive charge; in the nucleus of an atom

_____________________________

The small central core of an atom______________________________

Science COS #1 Voc

ElementsA substance that cannot be broken apart by another substance

The force that hold two atoms together is a chemical bond.

Two or more atoms that are bonded together form a molecule.

Some are made up of only one type of atom but most are made up of two or more different types of atoms bonded together.

Molecules= Two or more atoms chemically combined

Compounds= Two or more different elements chemically combined

Read E14-15

• Support Mendeleyev’s decision to create the periodic table. Use 2 details from the selection in your answer.• Mendeleyev arranged the elements by increasing atomic numbers

and are arranged in columns with similar properties.• The current periodic table is a standardized table for the entire world.

Read E16 : Explain the layout and meaning of each part of the square on the periodic table.

• Atomic number = the number of protons in the element• Atomic mass – number of

protons and neutrons• Equal number of protons and

electrons

6 – atomic number

C –element Symbol

Carbon – element name

Activity

• Choose and create a model for an element, showing the protons, neutrons, and electrons.• Atomic number 1-36 (not Carbon)

• Red – protons• Blue – neutrons• Yellow – electrons

• Chemical Elements.com - An Interactive Periodic Table of the Elements

• Level I – 2 electrons• Level 2 – 8 electrons• Level 3 – 18 electrons

Read E 17 – 20 and complete the graphic organizer

Category

Properties

5 Examples

• During the California gold rush, miners needed a way to remove Gold from a mixture that also contained dirt and sand. • Gold can be separated from other materials in a

mixture because of its density. (It has a higher density than most other materials including fool’s gold.)• They used the method of panning using a shallow pan

and water. Because gold is more dense, it stays in the bottom of the pan when the less dense materials (water, dirt, sand) are poured off.

Gold and Density

CompoundA pure substance made up of 2 or more elements that are chemically

combined

Read E26-27: Combining Elements

• Most common compound is water = 2 hydrogen atoms + 1 oxygen atom.• When molecules combine they take on different chemical properties

from the individual molecules.• Many compounds are found in nature and many more have been

created in the laboratory.• Compounds can be made form 2 or more molecules joining together.

Common Compounds

• Carbon dioxide = 1 carbon + 2 oxygen• Iron Oxide (rust) = 2 iron + 3 oxygen• When water is added to steel rust forms.• Why do you think metal near the ocean rusts faster?

Read E28: Chemical reactions

• Chemical reaction – a process in which one or more substances are changed into one or more different substances.• You can break down compounds into simpler substances by using

heat. One molecule is released while another is left behind.• Bottom of E28

• Simpler substances can also be combined to form a more complex substance.• Liquid hydrogen and oxygen are combined in rocket engines. The

combination produces steam which pushed the rocket off for the launch.

• Energy is required to combine or break compounds.

E 29-31: Formulas

• Discuss “Making a Compound” on top of E29• Chemical formula – a shorthand way to describe a compound using

chemical symbols and numbers.• The number on the lower right hand side of the symbol is called the

script and tells how many of that molecule is in the compound.

Activity

• Create a chart of some common compounds (use pages 29-31) showing • Compound Chemical formula Picture representation

• Math Mini Lesson• The chemical formula for baking soda is NaHCO3

• How many of each type of atom are in 4 molecules of this compound?

Review

• Know voc• Changes in atom model• Label periodic square• Know periodic categories, properties and examples• Chemical reactions and formulas• Atom – molecule - compound