1.2 Atomic Theory

What is smallest unit of matter ?

• The atom

What did the Ancient Greeks learn in 490-460 BCE?

• Believed that all the substances in the world were made from a combination of the fundamental elements- Earth, Air, Fire, Water

• Democritus believed that matter was composed of tiny indivisible particles called Atomos (Greek for indivisible)

What did John Dalton learn in 1803?

• “Dalton’s Atomic Theory”

• 1. Matter consists of definite particles called atoms

• 2. Each element is made up of its own type of atom

• 3. Each element has different properties

• 4. Atoms cannot be created, destroyed, subdivided

• 5. Atoms of two or more elements can combine in constant ratios to form new substances called compounds

What did J. J. Thomson learn in 1893?

• Discovered the presence of particles within the atom

• The atom is a positively charged sphere with negatively charged particles embedded within it (electrons)

• Chocolate chip cookie!

What did Ernest Rutherford learn in 1911?

• The atom must contain a relatively tiny positively charged centre called the nucleus

• Nucleus is composed of positively charged particles called protons

• Electrons are found in empty space

What did Niels Bohr learn in 1911?

• Electrons exist in orbits/energy levels as they go around the nucleus

What did James Chadwick learn in 1932?

• Discovered a dense, chargeless particle within the nucleus called the neutron

What was the main flaw in Rutherford’s model of the atom?

• The unorganized view of the electrons spinning around the nucleus

“The electromagnetic spectrum puts all types of radiation in order based on-”

• “-their wavelength”

Can you see all types of electromagnetic energy? Give examples

• No

• Visible light (the light you see every day)

• Radio waves, X-rays

The visible spectrum comprises what?

• The colours seen when sunlight passes through a prism

When colours from a prism blur together in an uninterrupted sequence, this is called what?

• Continuous

If you heat a sample of a pure element, what will you see?

• A distinctive pattern of lines

• Patterns are specific to the element

Describe light in relation to electrons

• When electrons are excited they move from a lower energy orbit to a higher one. When it drops back, the atom releases energy in the form of light!

What is the name for the lowest energy state of a system like an atom?

• Ground state

When different types of matter are burned at high temperatures, what’s cool about their flames?

• Produce flames of different colours

Define flame test

• Qualitative analysis technique

• Helps to determine the presence of a particular metal in an unknown sample by exposing the sample to high temperatures

What colour is calcium?

• Yellow

What colour is Copper?

• Green

What colour is Lead?

• Blue

What colour is Lithium?

• Pink

What colour is Potassium?

• Purple

What colour is Sodium?

• Orange

What are 4 distinct properties elements have?

1. The colour of the flame produced in a flame test

2. The temperature at which it boils

3. The temperature at which is melts

4. Its density

The distinct properties elements have can be useful for what?

• Can be used to identify unknown elements in an experimental setting

What is the melting point, boiling point, flame test result, and density of Potassium?

• Melting point: < 100^oC

• Boiling point: > 700^oC

• Flame test: purple

• Density: > 0.8 g/cm³

What is the melting point, boiling point, flame test result, and density of Lithium?

• Melting point: < 200^oC

• Boiling point: > 1000^oC

• Flame test: pink

• Density: < 0.61 g/cm³

What is the melting point, boiling point, flame test result, and density of Sodium?

• Melting point: < 100^oC

• Boiling point: > 800^oC

• Flame test: orange

• Density: < 0.1 g/cm³

What is the melting point, boiling point, flame test result, and density of Calcium?

• Melting point: 842^oC

• Boiling point: 1484^oC

• Flame test: yellow

• Density: 1.526 g/cm³

What is the maximum amount of electrons the first and second orbits are allowed to have?

• First: 2

• Second: 8

In what direction do you add electrons on the second and subsequent orbits?

• Start at the top, proceed clockwise, then begin pairs

A pure sample of an element contains how many types of atoms?

• One

Do all atoms in a pure sample of an element have the same number of protons?

• Yes

Elements on the periodic table are arranged by their-

• Atomic number

The atomic number of an element is equal to what?

• The number of protons (and electrons) in one of its atoms

Atomic mass is the sum of what?

• Protons + Neutrons

Define isotopes

• Atoms that are the same element but have different masses because they have a different amount of neutrons

Compare the protons and neutrons of Nitrogen-14, Nitrogen-15, Nitrogen-16

• Protons: same. All have seven protons

• Neutrons: increases. Being with seven and increases by one

Does a change in the number of neutrons change the atomic number? What about the mass?

• No

• Yes

“The atomic number represents the number of _____ that the atoms has”

• “-protons”

Does the number of protons remain seven in all isotopes of nitrogen?

• Yes

“The most stable kind of atom is considered-”

• “-electrically neutral”

What does ‘electrically neutral’ mean? This results in a net charge of what?

• When an atom possesses an equal number of protons (+) and electrons (-)

• Net charge of 0

If an atom possesses more or fewer electrons (-) than it does protons (+), what is it called?

• An ion

Are ions electrically neutral?

• No

“An ion is made by-”

• “-adding or removing electrons (-) from an atom”

In standard atomic notation, label X, A, Z

• X: the symbol for the element

• A: the atomic number

• Z: mass number

Describe what you see in standard atomic notation

• N: the symbol for Nitrogen

• 7: the atomic number of Nitrogen

• 14: the mass number of Nitrogen

Describe what you see in standard atomic notation

• F: Fluorine ion

• 9: atomic number

• 19: mass number

• ^-1: means it has gained an electron (-)

In standard atomic notation, what do square brackets mean?

• Indicate it’s an ion

In standard atomic notation, what does the ⁺² mean? Is this an ion?

• Two electrons (-) have been removed

• Yes

What is the standard atomic notation of Phosphorous-33?

With a stable atom, what is cool about protons, electrons, atomic number?

• They are all the same number

• Protons = Electrons = Atomic number

What is the formula to get the number of neutrons?

• Atomic Mass - Atomic Number

When drawing a Bohr-Rutherford diagram for an ion, what must you remember?

• To put brackets around it with the number of gained or lost electrons

“The periodic table is mainly arranged in _____ (from left to right) in order of increasing number of _____”

• “rows”

• “protons”

In the periodic table, columns (vertical) can also be called what? What about the rows?

• Families is vertical

• Periods is horizontal

What makes fireworks launch into the sky?

• A lift charge made of gunpowder rapidly burns and creates a massive rush of hot, expanding gases

What are fireworks packaged in?

• Paper, pasteboard, cardboard tubes, cardboard spheres, sometimes plastic

What metals are used in fireworks? Why?

• Strontium, Lithium for colours, Aluminum, Magnesium for flashes

• To create specific colours, bright flashes, sparks, special effects

Define what authority means when evaluating sources of information

• Considering who created the source

• Reputation and background

• Degree to which they’re experts in the field

Define what currency means when evaluating sources of information

• When the source was created

• Most recent is usually best

• Sometime need to find a course from a particular time period

Define what integrity means when evaluating sources of information

• Why the source was created

• How evident these reasons are

• What are their intentions

Define what relevance means when evaluating sources of information

• How practical/applicable the information is to the research

Define what validity means when evaluating sources of information

• Where the author gets their information

• How accurate the information is

• How well it’s supported