definitions Flashcards
atoms
Atoms are the smallest particles that make up matter.
atoms contain what?
Atoms contain sub-atomic particles – electrons,
protons and neutrons.
What is at the center of an atom?
At the center of an atom is the nucleus. The neutrons
and protons are found inside the nucleus.
what are protons?
PROTONS – are sub-atomic particles they are positively charged and have a
mass of 1 unit.
protons are found inside the nucleus of an atom
what are neutrons?
NEUTRONS – sub-atomic particles that are neutral (have no charge) and have a mass of 1 unit. neutrons are found inside the nucleus of an atom
electrons, what are they? and where are they found?
Orbiting the nucleus in shells
ELECTRONS – orbit the nucleus in fixed energy levels or shells and they are negatively charged and are
considered to have a mass of 1/1840
USES OF RADIOACTIVE ISOTOPES
cancer treatment
carbon dating
power source for heart pacemakers
detection of leaks
ph scale
The pH scale is a number scale from 0 to 14 that indicates how acidic or alkaline a
substance is by nature.
acidic substances
have pH values that are less than 7 . the closer the pH value is to 0, the more acidic the substance
alkaline substances
have pH values greater than 7. the closer the pH value is to 14, the more alkaline the substance
how can the acidity or alkalinity of a substance be determined?
an indicator
a pH meter
what are indicators
Indicators are dyes that when inserted in an acidic solution turn a/one colour and when inserted in and alkaline solution change another colour.
they can be used in liquid form, absorbed onto a piece of absorbent paper or strips(litmus paper)
pH meter
a device used to determine precisely the pH value of a substance. It gives an accurate pH value which is read directly on the pH meter
What are acids?
Acids are defined as substances that yield H+ ions as the only
positive ion when in solution.
characteristics of acids
Clear, colourless liquids Sour Corrosive Turn blue litmus red Have pH values less than 7 Can conduct electricity
classification: origin of acids- mineral acids
Mineral acids are the acids commonly used in the lab and they are considered as being STRONG acids. hcl, hno3, h2so4
origin of acids- organic acids
Organic Acids are acids that are usually found in nature and are considered as being WEAK
acids.
classification: strength of acids- strong acid
a STRONG acid is an acid that dissociates completely or almost completely into ions when in solution.
That is, all or most of the acid molecules dissociate to form the cation and the anion.
weak acid
an acid that dissociates to a small extent when in solution
classification: basicity
The basicity of an acid is the number of H + ions each molecule of an acid yields when it
dissociates.
monobasic acids
a monobasic acid is an acid that yields one h+ ion per molecule
h+ + cl-
hcl, hno3, ch3cooh
dibasic acids-
yields only two h+ ions per molecule
h2so4
tribasic acids
yields three h+ ions per molecule
h3po4
classification: concentration dilute and concentrated
A dilute acid is an acid that has a small number of acid molecules dissolved in a given volume of
water.
A concentrated acid will have a large number of acid molecules dissolved in a given volume of
water.
isotopes
atoms of the same element that have the same number of protons but different numbers of neutrons
radioactive isotopes
radioactive isotopes are unstable isotopes that spontaneously spilt releasing large amounts of radiation, in the form of beta and alpha particles as well as y rays
characteristics of isotopes
isotopes will have the same number of electrons
isotopes will have the same atomic number but different mass numbers
isotopes will show the same chemical properties
isotopes will have different physical properties
ph chart
when an idicator is used you can compare the colour change to a pH chart to approximate the value of a given substance
universal indicator
used to tell how acidic or alkaline a substance is
ram- relative atomic mass
rmm- relative molecular mass
ionic bonding- bonding of ions
physical properties of a compound are?
melting and boiling point- high melting point and boiling point
electrical conductivity- conducts electricity when molten or dissolved in water
solubility- soluble in water, insoluble in organic solvents
STATE AT ROOM
TEMPERATURE- form Crystalline solids
noble gases
he, ne, ar are all known as noble gases or inert gases because they are unreactive. they have full outer shells
water crystallisation
Sometimes, as crystals of a salt form, water molecules become trapped inside the lattice.
ionic substances
Composed of ions held together by strong ionic
bonds.
cation and anion
when an atom loses electrons it becomes positive
gains electrons it becomes negative
how r compounds formed
when atoms of elements are chemically combined
salts
when acids react with certain chemicals, the H +ion is replaced by a new cation and the substance formed is called a salt.
A salt is a substance produced when some or all of the replaceable H+ (hydrogen) ions of an acid have been replaced by a metal cation or ammonium ion
Mass number
The total number of protons and neutrons in the nucleus of one atom of an element
Atomic number
The number of protons in the nucleus of one atom of an element
position of Atomic number
At the bottom
position of Mass number
At the top
The atomic number and the number of protons are equal to the number of…
Electrons surrounding the nucleus of on atom of an elemntb
Isotopy
The occurrence of atoms of a single element that have the same number of protons in their nuclei but different numbers of neutrons
Types of isotopes and their isotopy
Cl- twice
C- thrice
Uses of radioactive isotopes
Carbon-14 dating- used to determine the age of plant or animal remains (organic material). Accurate up to 60,000 yrs. If the percentage of carbon is high, the remains are young, if the percentage of carbon is low, the remains are old.
Cance treatment (radiotherapy)
Cancerous cells in tumors can be destroyed by focusing a beam of radiation from radioactive cobalt- 60 at the cells. Or idione-131 can be injected directly into a cancerous tumor
Heart pace makers
Powered by batteries containing plutonium-238. Should last the entire of the patient’s lifetime as half the battery life of a plutonium battery is 87 yrs
Mass of electron
1/1837
Charge of electron
-1
Mass of neutron
1
Charge of neutron
0 (neutral)
Mass of proton
1
Charge of proton
+1
