Forensics Chemistry

Question 1

What is an atom?

Answer 1

The smallest part of. Chemical element.

Question 2

What is an element?

Answer 2

A substance consisting of atoms which all have the same number of protons.

Question 3

What is a proton?

Answer 3

A subatomic particle with a positive charge and is equal to the magnitude of an electron.

Question 4

What is a neutron?

Answer 4

A subatomic particle with the same ass as a proton. It is present in all atomic nuclei but hydrogen.

Question 5

What is an electron?

Answer 5

A subatomic particle which has a negative charge.

Question 6

What is an atomic number?

Answer 6

The number of protons in an element. It determines an elements place on the periodic table.

Question 7

What is an isotope?

Answer 7

Types of the same element that have the same number of protons but a different number of neutrons.

Question 8

What is a mass number?

Answer 8

Th total number of protons and neutrons in a nucleus.

Question 9

What is relative atomic mass?

Answer 9

The ratio of average mean mass of one atom of an element.

Question 10

What is the maximum number of electrons in the 1st, 2nd and 3rd shell?

Answer 10

1st shell= 2 electrons
2nd shell = 8 electrons
3rd shell = 18 electrons

Question 11

What the number of electrons in outer shell and the number of shells determine?

Answer 11

Number of electrons determine the elements group.
The number of shells determines the elements period.

Question 12

What is a compound?

Answer 12

A substance that is composed of two or more separate elements.

Question 13

What is a molecule?

Answer 13

A group of toms bonded together, representing the smallest es fundamental unit of a chemical compound that can take part in a chemical reaction.

Question 14

What is an ion?

Answer 14

An atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

Question 15

What is a monatomic ion?

Answer 15

Formed by the gain or loss of electrons to the valence shell (the outermost electron shell) in a single atom.

Question 16

What is a polyatomic ion?

Answer 16

Formed by the gaining or losing of elemental ions such as a proton.

Question 17

What is the equation for moles?

Answer 17

Mass= Mr X Mol

Question 18

What are the diatomic elements?

Answer 18

Hydrogen
Nitrogen
Fluoride
Oxygen
Iodine
Chlorine
Bromine

Question 19

What is an empirical formula?

Answer 19

Shows the simplest whole number ration of atoms of each element in a compound.

Question 20

What is molecular formula?

Answer 20

It shows the number and type of atoms present of each element present in a compound.

Question 21

What should an empirical formula method look like?

Answer 21

Substance/ element / element
1. Elements
2. Mass of each element
3. Atomic mass
4. Mass/atomic mass (mol)
5. Ration (divide both numbers by smaller one)
6. Formula

Question 22

What is stoichiometry?

Answer 22

The ration of the amount of moles of each substance in a chemical reaction. (The big number)

Question 23

What is the method for reacting mass calculations?

Answer 23

1. Write a balanced equation
2. Convert mass to number of moles.
3. Find mole ratio from equation
4. Convert number of moles to mass

Question 24

Equation for calculations involving solutions.

Answer 24

Moles =concentration X volume

Question 25

What is the equation for percentage yield?

Answer 25

Percentage yield = actual yield/ theoretical yield x 100

Question 26

Why is the theoretical yield not always achievable?

Answer 26

1. The reaction may not have gone to completion 2. Other reactions (side reactions) may have occured. 3. Purification of the product may have resulted in loss of product 4. Some might be left in equipment.

Question 27

What is an orbital?

Answer 27

A region within an atom that can hold up to two electrons with opposite spin.

Question 28

What is a sub-shell?

Answer 28

A group of orbitals of the same type within a shell.

Question 29

What is an electron shell?

Answer 29

A group of atomic orbitals with the same principal quantum number. Also known as a main energy level.

Question 30

What is a principal quantum number?

Answer 30

The shell number.

Question 31

Explanation paragraph on orbitals.

Answer 31

Electrons are found in orbitals. An orbital is a space that can hold up to two electrons. They can be empty, hold one or hold two electrons. there are for types of orbitals. They are different shapes. A collection of the same type of orbital at the same energy level is called a sun shell. All of the sub shells with th same principle quantum number (starting number) form a shell.

Question 32

What are the four types of orbitals?

Answer 32

F sub shells- contains 7 orbitals & holds 14 electrons. D sub shells- contains 5 orbitals &holds 10 electrons P sub shells- contain 3 orbitals & holds 6 electrons S sub shells- contains 1 orbital &hold 2 electrons.

Question 33

What is ionisation?

Answer 33

When an atom loses an electron from its outer shell.

Question 34

What is first ionisation energy?

Answer 34

The energy required to removes 1 electron rom each atom in only mole of gaseous atoms of an electron to form on ole of gaseous 1+ ions

Question 35

What is electron affinity?

Answer 35

The change in energy when 1 electron is gained by each atom in one mole of gaseous ato of an element to form one mole of gaseous 1- ions.

Question 36

Wh at is ionic bonding?

Answer 36

Th electrostatic attraction between positive and negative ions. Between a metal and non-metal.

Question 37

What are the properties of ionic bonding?

Answer 37

-The higher the charge, the stronger the attraction, the higher the melting/boiling point. -the smaller the ions, the closer the outer electrons are to the nucleus, the stronger the attraction, the higher the melting/boiling point.

Question 38

Can ionic bonds produce electricity?

Answer 38

-A substance can conduct electricity if it contains charged particles such as ions and electrons. These particle are free to move from place to place - An an ionic compound can conduct electricity when it has melted to form a liquid or it has dissolved in water to form an aqueous soloution. -Ionic compounds conduct electricity when melted or in solution. They are insulator when solid.

Question 39

What is covalent bonding?

Answer 39

The strong electrostatic bond between a shared pair of electrons and the nuclei of bonded atoms. One shared pair f electrons is called a single covalent bond. A pair of non-bonding electrons is called a lone pair.

Question 40

What is dative covalent bonding?

Answer 40

In a dative covalent bond, one of the atoms supplies both shared electrons for the covalent bond.