Lecture 2 - Basic Chemestry Flashcards Preview

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element

A form of matter indivisible by normal means.

1

What are the four main elements that make up the human body?

oxygen, hydrogen, carbon, nitrogen

2

compound

Two or more different elements

3

atom

Smallest particles that retain properties of an element

4

Atoms are made of what subatomic particles? What are their respective charges?

protons (positive)
neutrons (neutral)
electrons (negative)

5

Which subatomic particle are represented by atomic numbers?

protons

6

isotope

Atoms of an element with a different number of neutrons, behave the same as the normal element in chemical reactions

7

What determines whether atoms will interact with each other?

The number and arrangement of electrons

8

Properties of electrons

Carry a negative charge
Repel one another
Are attracted to protons in the nucleus
Move in shells (volumes of space surrounding the nucleus)

9

List the number of electrons in the first three shells of an element

First shell: 2
Second shell: 8
Third shell: 8

10

chemical bonds

A union between two atoms

11

valence shell

The outermost shell of an atom.

13

List the three types of bonds, in order of strength, from strongest to weakest

ionic
covalent (either polar or nonpolar)
hydrogen

14

Which bonds are held together by charge differences in elements?

ionic bonds, hydrogen bonds

15

Which bonds are held together by the sharing of electrons?

covalent bonds

16

What is the difference between polar and non-polar covalent bonds?

In polar covalent bonds, the electrons are not shared equally amongst the elements, with electrons spending more time near the larger nucleus, resulting in a charge differential.
In non-polar covalent bonds, the electrons are shared equally, resulting in no charge difference across the element

17

If both ionic and hydrogen bonds are held together by charge differentials, what is the difference between them?

Ionic bonds are created though the exchange of an electron, turning two previously neutral elements into a positive and negative one, strongly attracting each other without sharing electrons.
Hydrogen bonds are created when a polar covalently bonded molecule is attracted to an oppositely charged atom.

18

ionic bond

One atom loses electrons, becoming a positively charged ion, while the atom that gains the lost electrons becomes negatively charged. The charge difference attracts these ions, they do not share the electrons afterwords.

19

hydrogen bond

Atom in one polar covalent bond attracted to oppositely charged atom in another such molecule or same molecule

20

List the properties of water

Cohesive - binds to itself
Adhesive - binds to other
Stabilises temperature
Expands when frozen
Capacity to dissolve substances

21

What are hydrogen ions?

Unbound protons that form when water ionises, a hydrogen wtom with no electron

22

What does pH measure?

The hydrogen ion concentration of a fluid

23

Describe the pH scale

A scale measured between 0 and 14, with 0 being the highest concentration of hydrogen ions and 14 being the lowest, each integer below 14 represents a 10-fold increase in the number of hydrogen ions present.

24

acid

Substances which donate hydrogen ions when dissolved in water, have a pH of < 7

25

base

Substances which accept hydrogen ions when dissolved in water, have a pH of > 7

26

covalent bond

Atoms share a pair or pairs of electrons to fill the valence shell

27

buffer system

A partnership between a weak acid and the base it forms when dissolved, working as a pair to counter shifts in pH, minimising the effects.

28

Identify the reactants and the products of this equation:
2 H2 + O2 -> 2 H2O

H2 and O2 are the reactants, the products are two molecules of water (2 H2O)

29

Why do water molecules form hydrogen bonds?

It is a polar molecule

30

What is an elect called that has lost an electron?

An ion