Science - Chapter 6 (Chemistry)

What is an atom?

• building block of matter

• smallest particle possible

What are molecules?

• more than one atom (plural)

What is an element?

• pure substance that consists of only one type of atom (same)

Example

1 carbon atom = C

2 oxygen atoms = 0₂

What is a compound?

• pure substance made up of two or more elements that are chemically combined (different)

• can be broken down into molecules

Example

2 hydrogen + 1 oxygen = H₂0 **NOTE: water is pure BUT has different types of atoms

Who invented the Chemical Symbols?

It was invented be a Swedish chemist, Jon Jacob Berzelius

What are the rules?

1. First letter of element name

   • Ex. C - carbon H- hydrogen

2. First two letter of element name

   • Ex. Ca - calcium He - helium

3. First & third letter of element name

   • Ex. Cl - chlorine Cr - chromium

4. First & later letters of Latin name

   • Ex. Cu - cuprum = copper

- Different Kinds of Elements -

Metals, Non-Metals, & Metalloids

Metals:

• conduct electricity & heat

• shiny

• malleable & ductile

• solid at room temperature (except mercury)

Non-Metals:

• does not conduct electricity & heat (insulator)

• not shiny

• brittle & not ductile

• solid, liquid, gas at room temperature

Metalloids:

• properties between metals & non-metals

• conduct electricity, NOT heat (semi-conductor)

• shiny or dull

• brittle & not ductile

• solid at room temperature

What is a chemical family?

It is a group of related elements sharing common chemical properties

Example: gold, silver, copper

Who is Demitri Mendeleev?

• made a card for each known element with it’s properties (only 63)

• arranged cards by increasing mass

• noticed group elements had similar physical and chemical properties

• predicted properties of undiscovered elements

• this formed a pattern periodically → periodic table

Name of the Chemical Families:

Alkali Metals (Group 1)

Alkaline Metals (Group 2)

Halogens (Group 17)

Noble Gases (Group 18)

Alkali Metals (Group 1)

• most reactive metals

• react quickly when exposed to air & water

Alkaline Metals (Group 2)

• 2nd most reactive metals

Halogens (Group 17)

• most reactive non-metals

Noble Gases (Group 18)

• inactive/does NOT react

• very stable

Column =

Group

Row =

Period

Find the element: Group 2 - Period 3

The element is Magnesium (Mg)

- Famous scientists and their theories of atoms -

Democritus (400 BCE)

• all matter can be divided into smaller and smaller pieces until it is a single invisible particle

• there are different sizes

• in constant motion

• separated by empty spaces (the void)

Aristotle (450 BCE)

• all matter is made up of four basic substances: earth, water, air, and fire

• four specific qualities - dry, wet, cold and hot

John Dalton (1807)

• all matter is made up of tiny, invisible particles called atoms

• all atoms of an element are identical

• atoms of different elements are different

• atoms are rearranged to form new substances in chemical reactions, but they are never created or destroyed

J.J. Thomson (1897)

• atoms contain negatively charged electrons

• since atoms are neutral, the rest of the atom is a positively charged sphere

• negatively charged electrons are evenly distributed throughout the atom

What 3 things did Ernest Rutherford (1909) discover?

Discovered metal atoms of gold have:

1) Nucleus - center of atom with positive charge

2) Electron Cloud - surrounds nucleus with negative charge

3) Most of the atom is empty space

What did James Chadwick (1932) discover?

Discovered that the nucleus also has a neutral particle with a mass called neutrons

What did Niels Bohr (1913) discover?

• electrons move rapidly around nucleus (orbit) in electron

• more energetic electrons, the further the shells

• each shell holds maximum amount of electrons

Bohr-Rutherford Atom Example:

What is a proton?

• found inside the nucleus

• has a positive charge (+)

• represented by “p” in the nucleus

  Example: 11P

What is an neutron?

• found inside the nucleus

• has a neutral charge (-)

• represented by “n” in the nucleus

  Example: 12N

What is an electron?

• found outside the nucleus

• has a negative charge

• represented by “ē”

What is a atomic number?

Number of protons/electrons in the nucleus

What is a mass number?

The number of protons + neutrons in the nucleus

How do you solve for the number of neutrons in an atom?

Number of Neutrons = Mass Number - Atomic Number

How to draw standard notation:

What are the patterns found in the periodic table?

• same period # have the same number of shells

• same group # have the same number of electrons in the outer shell

- Alkali Metal → 1 electron

- Alkaline → 2 electrons

- Halogens → 7 electrons

- Noble Gases → Full shell (2 electrons of 8 electrons)

• smaller period # → fewer number of shells

• smaller group # → smaller radius of atom

Elements with electrons(s) further from the nucleus are more reactive

What is charcoal?

• shapeless, disorganized arrangement of carbon atoms which creates a soft black solid

• forms an unending structure

What is graphite?

• the arrangement is organized

• each carbon atom joins with three other carbon atoms to form a sheet of interconnected hexagons

• flat sheets are loosely layered on top

What is diamond?

• due to extremely high pressure, carbon atoms arrange themselves into regular patterns

• they are interconnected in three dimensions