SNC 2P - Chemistry - Atomic Structure & the Periodic Table

The Bohr-Rutherford Atom

The Bohr-Rutherford atom consists of a central nucleus, surrounded by progressively larger concentric circles.  This model can be likened to the solar system.  

 

Subatomic Particles

There are three subatomic particles, that combine in various amounts, to create an element.  

 

Standard Atomic Notation (^A_ZX)

Standard atomic notation is one method used to communicate the components of a given element.

 

Bohr – Rutherford Diagrams

Bohr- Rutherford diagrams (or Bohr diagrams, for short) are used to illustrate the components of a given element.

Recall:

• typically, we only draw these diagrams for the first twenty elements on the Periodic Table
  
• the maximum number of electrons in each shell is 2, 8, 8, 8 - moving outward from the nucleus
• in the second shell and beyond, the electrons are never doubled up until each of the four spaces already hold one electron

 

Lewis Diagrams

Lewis diagrams consist of the element symbol with the appropriate number of dots to represent valence electrons.

Recall:

• these diagrams can be drawn for any element on the Periodic Table
  
• we only show the outermost (valence) electrons 
• electrons are never doubled up until each of the four spaces already hold one electron
• as we move across the tall columns on the Periodic Table (from left to right), the number of valence electrons follows this pattern: 1, 2, 3, 4, 5, 6, 7, 8
  

 

Mendeleev’s Periodic Law

Mendeleev's periodic law states, "If the elements are arranged according to their atomic mass, a pattern can be seen in which similar properties occur regularly."

Mendeleev's journey to create the periodic table is fascinating.

 

Modern Periodic Table

Modern periodic law states, "If the elements are arranged according to their atomic number, a pattern can be seen in which similar properties occur regularly."

 

Periodic Table

Label:

➤ staircase

➤ periods (rows); period numbers (1 to 7)

➤ families/groups (columns); group numbers (1 to 18)

• alkali metals
• alkaline earth metals
• transition metals
• aluminum group
• carbon group
• pnictogens
• chalcogens
• halogens
• noble gases
• lanthanides
• actinides

 

Metals, Non-metals & Metalloids

• metals – malleable, ductile, conductive, shiny (ex. Na, Pb, Hg)
• non-metals – brittle, non-conductive, dull (ex. N, S, Ar)
• metalloids – have properties of both metals and non-metals (ex. Te, Si, Te)

 

Homework:

Draw the Bohr diagrams for the first twenty elements.

Draw the Lewis diagrams for the first twenty elements.

 

Answer Key:

 

SNC 2P - Chemistry - Matter, Properties & Changes

Matter

Matter is anything that has mass & volume.

 

Changes of State

 

Classification of Matter

 

Physical Property

A physical property is a property that can be determined without altering the chemical composition of the material (ex. colour, odour, melting point).

Quantitative Physical Property

A quantitative physical property is a measurable property that has a number and a unit (ex. density, mass).

Qualitative Physical Property

A qualitative physical property is simply a description that does not have a measurement (ex. colour, odour).

 

Chemical Property

A chemical property is a property that describes how matter behaves in the presence of other substances or when subjected to heat, light or electricity (ex. iron reacts with oxygen to form rust).

 

Physical Change

A physical change is a change in which the chemical identity or composition of the sample of matter remains the same (ex. cutting wood, all changes of state, dissolution).

 

Chemical Change

A chemical change is a change in which at least one new substance is formed (ex. burning wood).

 

Homework: 

Using the periodic table, let's make like an element and "zinc" about the elements.

 Also, complete the following worksheet (the key is below the worksheet, so you can check your answers):

 

SNC 2P - Physics - Optics Review

Review:

 Answers: 

 

SNC 2P - Physics - Diverging Lenses

Lenses

We use lenses everyday in our daily lives.  Check out this video for some examples.

 

Diverging Lenses

A diverging (concave) lens causes parallel rays to diverge after passing through the lens.  The rays appear to be coming from the focal point on the side from which the rays originate.

 

Ray Diagram for Concave Lenses

To see the image, you must put your eye in the path of the diverging rays.  If you place your eye where the rays are still converging, you will not see the image.

For a diverging lens, the rays parallel to the PA are refracted so that they appear to be diverging from the focal point on the side of the lens where they began.

 

Ray Diagram for Concave Lenses

To determine the kind of image formed by a convex lens, draw light ray diagrams.

Watch this video (start at 1:05) to see ray diagrams being drawn.

 

Practice Answer Key:

 

Question of the Day #13:  Draw the ray diagram and state the image characteristics (SALT).

 

 

SNC 2P - Physics - Converging Lenses

Lenses

We use lenses everyday in our daily lives.  Check out this video for some examples.

 

Converging Lenses

A converging (convex) lens is called a converging lens because any set of parallel rays that strike the lens will converge at a single point on the opposite side of the lens.

  

Properties of Convex Lenses

The principal axis (PA) runs through the centres of curvature.

The upright axis perpendicular to the PA is the vertical axis (V).

Unlike mirrors, lenses have two spherical surfaces, two radii of curvature and the light passes through a refracting medium in both directions.

Parallel rays that pass through a converging lens converge to a point on the other side of the lens.  This is the focal point (F) (there is a focal point on each side).

The distance from the vertical axis to the focal point is the focal length (f).

 

To see the image, you must put your eye in the path of the diverging rays.  If you place your eye where the rays have yet to converge, you will not see the image.

 

 

Ray Diagram for Convex Lenses

To determine the kind of image formed by a convex lens, draw light ray diagrams.

Watch this video (start at 1:55) to see ray diagrams being drawn.

 

Practice Answer Key:

 

Question of the Day #12:  Complete p. 355 # 7.  Send me a picture of your answer on Edsby.
 

 

SNC 2P - Physics - Refraction Applications

Partial Refraction

When looking at a body of water (like a lake or a swimming pool) on a sunny day, sometimes you are blinded by the glare of the Sun off the water.  Light passes through the water, as well as being reflected.

When light strikes any interface between two media, some of it reflects back, while some of it refracts through the second medium.

When light travels from air to water, some light reflects from the surface and some light travels into the water and refracts.

This is the partial reflection and refraction of light.

 

 

Conditions for Total Internal Reflection

In diagrams A and B, the angle of refraction is increasing more rapidly than the angle of incidence.  In diagram C, the angle of refraction has reached 90°, making the angle of incidence the critical angle.  At all angles beyond the critical angle, as in diagram D, all light is internally reflected.

Notice that the refracted light bends away from the normal. 

For all angles of refraction up to and including 90°, the light is reflected and refracted at the same time.

The amount of reflected light gradually increases and the amount of refracted light gradually decreases as the angle of incidence increases.

The angle of refraction increases more rapidly than the angle of incidence.

The angle of incidence for which the angle of refraction equals 90° is called the critical angle.

When angle of incidence is greater than the critical angle, all the incident light is completely reflected.

The boundary now behaves as if it were a perfect mirror and there is total internal reflection.

This phenomenon is the reason why diamonds sparkle. 

Watch this video (watch until 6:07) for more info.

 

Fibre Optics

Read p. 339.

Question of the Day #11:  List two reasons why optical fibres are preferred over copper wires for many types of communication.