SCH 4U ( Answers) UNIT 2 TEST Structure AND Properties Bolzon PDF

Preview

Summary

chem...

Description

UNIT 2 TEST STRUCTURE AND PROPERTIES SCH 4U - Online Student Name: _______________________________________ Date: July 9th, 2020 (This is for teacher use only… it’s how I mark you…) Curriculum Expectations

Assessment

C2. investigate the molecular shapes and physical properties of various types of matter;

Out of 32

C3. demonstrate an understanding of atomic structure and chemical bonding, and how they relate to the physical properties of ionic, molecular, covalent network, and metallic substances.

Out of 21

PART A - Multiple Choice (4 marks: C3) Highlight the letter for your answer for each question 1) Sodium ion has the same electronic configuration as a neutral atom of: a) Oxygen b) Magnesium c) Neon d) Fluorine 2) Bromine ion has the same electronic configuration as a neutral atom of: a) Selenium b) Lithium c) Chlorine d) Krypton (THIS WAS AN ERROR - FREE MARK FOR EVERYONE; bonus if you told me it was Krypton) 3) The maximum number of electrons which can occupy the second energy level of any atom is: a) 8 b) 2 c) 9 d) 18 4) In a chemical reaction a non-metal atom usually: a) gains protons. b) loses protons. c) gains electrons. d) loses electrons.

PART B - Matching (6 marks: C3) Match each of the following terms with its appropriate descriptions using the LETTER associated with the word A. Transition Metals B. p-orbitals

C. Alkali Metals D. Proton

E. d-orbitals F. Neutron

Letter Answer

Description

C

The elements which have “s” valence electrons

B

Dumbbell like orbitals that hold 6 electrons

D

Positive particle that determine an element's identity

E

Five types of orbitals that can hold up to 10 electrons

A

The elements which have “d” valence electrons

F

Changing the number of this would change the mass of the element

PART C - Short answer 1) Explain what is occurring in a covalent (molecular) bond at the microscopic level. Why do covalent bonds occur? (2 marks: C3) A covalent bond is a bond that occurs between two nonmetal atoms.There are two electrons being shared within this bond. Covalent bonds can be polar (unequal sharing) or non-polar (equal sharing). Covalent bonds occur to help stabilize and satisfy each elements desire for a full octet 2) Explain why trigonal planar is a nonpolar molecule but trigonal pyramidal is polar. (2 marks: C2) Trigonal planar is nonpolar due to the overall shape of the molecule having the bonds on the same PLANE. This allows for any polarized bonds to cancel the overall dipole moment. This leaves the molecule with no overall polar charge, leaving it non polar. Trigonal pyramidal is polar due to the lone pairs on the center atom pushing down the bonding pairs to create a pyramid type shape. Since these bonds are all overall pointing upwards, if the bonds are polar, the molecules will be polar. 3) Choose ONE (1) to explain: Hund’s Rule or AUFBAU or Pauli Exclusion Principle. (2 marks: C2) a) Connect this concept to a REAL-LIFE example to illustrate the rule. Explanation: VARIES Real life Example:

PART D - Long Answer 1) Identify the following atoms or ions from the following electron configurations: (4 marks – C3) a) atom: 1s22s2 2p6 3s2 3p6 4s2 3d10  4p1 ______Ga_______ 2 b) atom: [Rn]7s ______Ra_______ 2 2 6 c) An ion with a 2- charge: 1s 2s 2p ______O_______ N  eutral oxygen: 1s22s2 2p4 + 2ed) atom: [Kr]5s2 4d7 ______Rh_______

2) The electronic configuration for a certain element is 1s2 2s2 2p6 3s2 3p6 4s2 3d9 . a) Identify the element.

(5 marks: C3)

Answer: COPPER (Cu) b) How many valence electrons are there for this element? Answer: 9e- (3d9 ) would also accept 11e- (9 d-electrons, plus 2 s electrons) THINK: Shorthand is [Ar]4s2 3d9 c) Give four (4) possible quantum numbers for an electron in the 3p6 orbital. Answer: n=3 l=1 ml = +1 ms = +1/4 d) What is the most common charge (number and sign) on this element? How do you know? Answer: (+1) this is since copper is a metal, therefore wants to lose electrons. *Sorry, this is actually something you didn’t learn. For those interested… Cu: 1s22s2 2p6 3s2 3p6 4s2 3d9 … but FULL or HALF-FULL orbitals are MOST stable, this causes the an s electron to be “promoted” to the d-ortibals: 1s22s2 2p6 3s2 3p6 4s1 3d10  .. now d is full and s is half full. If we 2 2 6 2 6 10 1 reorder by energy level we get 1s 2s 2p 3s 3p 3d 4s … so we lose the one electron from the s since it has the highest energy and these always get lost first! e) Why is this element's electron configuration sometimes seen written as 1s2 2s2 2p6 3s2 3p6 3d94s2? Answer: According to AUFBAU, electrons are filled from lowest energy to highest. This means that 4s would be the highest energy therefore written at the end.

3) Complete the following table for VESPR theory. (24 marks: C2) *Upload any drawings into dropbox* On your paper please write the compound formula AND “Long answer: Part D question 3” Compound

Lewis structure (Upload drawing into dropbox)

Family Name

Molecular Shape

General Formula

Polarity

BrF5

Octahedral

Square pyramidal

AX5E

Polar

SiCl4

Tetrahedral

Tetrahedral

AX4

Non-polar

BBr3

Trigonal Planar

Trigonal Planar

AX3

Non-polar

IF3

Trigonal bipyramidal

T-shaped

AX3E2

Polar

XeF4

Octahedral

Square planar

AX4E2

Non-polar

SeCl4

Trigonal bipyramidal

Seesaw

AX4E

Polar

4) Choose TWO (2) compounds from above and determine if they are a POLAR or NONPOLAR molecule. Draw the dipoles on the lewis structure to illustrate your answer. (4 marks: C2) Hint: Remember what we talked about on the review about e lectronegativity and the overall molecule shape. *Upload drawings into dropbox* On your paper please write the compound formulas AND “Long answer: Part D question 4” For this you needed to show the dipoles pointing towards the more electronegative atom, the shapes, AND put a small discussion of WHAT those dipoles mean. Then state polar or nonpolar. 2 mark for dipoles 1 mark for polar/non-polar 1 mark for explanation...