4-1 Notes - Atoms

Basic Units of MatterChapter 4, Lesson 1

Atoms and their Parts

Matter is anything that has mass and takes up space (such as solids, liquids and gases)

Sound, heat and light are not matter - they are forms of energy.

Atoms and their Parts

An atom is a small particle that makes up all matter.Atoms are mostly empty space surrounding a massive central region of the atom called the nucleus.Atomic-force microscopes help us visualize the surfaces of atoms.

Atoms and their Parts

Atoms contain three kinds of particles: two are in the nucleus, and one is outside the center of the atom.

Atoms and their Parts

Protons are positively charged particles in the nucleus.Neutrons are neutrally charged (no charge) particles in the nucleus.Electrons are negatively charged particles that move in the space outside the nucleus.

Atoms and their Parts

Most of an atom’s mass comes from the protons and neutrons.An electron is much smaller - it has about 1/2,000 the mass of a neutron or proton.

Atoms and their Parts

Atoms and their Parts

Democritus

He was a Greek philosopher who lived from 460 – 370 BCE.

Democritus

Proposed that atoms were small, solid spheres.First coined the word “atom,” based on the Greek word “atoma,” which means “indivisible” or “uncuttable.”

Democritus

Democritus described the atom as indivisible, meaning it was the smallest possible piece of matter that could not be cut into smaller pieces.

Lavoisier

Antoine Lavoisier was a French scientist who lived from 1743-1797.

Lavoisier

He conducted experiments that led to the Law of Conservation of Mass.

Lavoisier

A chemical reaction rearranges atoms of one substance into another substance with different properties.

Lavoisier

This law says that in any chemical reaction, the total mass of the starting materials is always equal to the total mass of the product.

Proust

J.L. (Joesph Louis) Proust was a French scientist who lived from 1754-1826.

Proust

He conducted experiments that led to the Law of Definite Proportions.

Proust

This law states that pure compounds always contain the same elements in the same proportions by mass.

Proust

Water’s formula is H2O which means there are two hydrogen atoms and one oxygen atom in every molecule of water.Water from your kitchen sink is the same as water from a glacier on Mars.

Dalton

John Dalton was an English schoolteacher and scientist who lived from 1766-1844.

Dalton

He did many experiments on gases that led to a new and more complete model of the atom.Dalton’s model had 5 major points.

Dalton

1. All matter is made up of atoms.

Dalton

2. Atoms are neither created nor destroyed in chemical reactions. (Law of Conservation of Mass)

Dalton

3. Atoms of different elements combine in whole-number ratios. (Law of definite proportions)

Dalton

4. Each element is made of a different type of atom.

Dalton

5. The atoms of different elements have different masses and properties.

Dalton

Dalton used symbols to represent different elements, making it easier to write and communicate about the elements.

Fe

Which is NOT a particle in an atom?

A positron

B neutron

C electron

D proton

4.1 Atoms—Basic Units of Matter

Which law states that the total mass of the starting materials equals the total mass of the product in a chemical reaction?

A Dalton’s atomic model

B the law of conservation of mass

C the law of definite proportions

D Democritus’ law

4.1 Atoms—Basic Units of Matter

____ make up the nucleus of an atom.

A Protons and electrons

B Neutrons and electrons

C Protons and neutrons

D Neutrons and photons

4.1 Atoms—Basic Units of Matter

Which particle has a positive charge?

A nucleus

B proton

C electron

D neutron

SCI 3.a

Who thought that atoms were very small, solid spheres?

A Dalton

B Rutherford

C Thompson

D Democritus

SCI 3.a