Chapter 1 & 2 Test Flashcards
Scientific Notation
a x 10* 1 ≤ a ≤ 10 * = # of decimal places moved * > 0 if decimal moves left *< 0 if decimal moves right
Scientific Notation Steps
- Move the decimal until there is ONLY 1 number to the left of the decimal
- Write this number down (but don’t include any unnecessary zeros) followed by “x 10 *” where * is the # of decimal places moved
Significant Digits
The # of digits that are known with certainty plus 1 that is uncertain
Rules For Counting Significant Digits
- All nonzero figures are significant
- All zeros between nonzero figures are significant
- When a decimal point is shown, zeros to the RIGHT of the nonzero figures are significant
- Zeros to the left of the first nonzero are not significant (add decimal if needed)
Rules for Adding and Subtracting Significant Digits
The final answer must have the same number of DECIMAL PLACES as the measurement with the LEAST # of DECIMAL PLACES
Rules for Multiplying and Dividing Significant Digits
The answer should contain no more SIGNIFICANT DIGITS than the measurement with the FEWEST # of SIGNIFICANT DIGITS
Rules for Rounding Off
- If the first digit to be dropped is <5, the PRECEEDING digit stays the
- If the first digit to be dropped is >5, the PREECEDING digit is increased by 1
- If the first digit to be dropped is 5 followed by only zeros, ROUND UP if the PRECEEDING number is ODD (483.5 —> 484) and LEAVE it the same if it is EVEN (482.5 —> 482)
Precision
Refers to the exactness of a measurement (the greater the number of significant digits —> the greater the precision
Accuracy
Refers to how close a given quantity is to an accepted value
Dimensional Analysis
A method of calculation in which both numbers and units are carried through the algebraic operation
Conversion factor
Ratios (fractions) comparing 2 units
Atom
The smallest particles of an element that still retains the identity and properties of an element
Atomic Number (Z)
Number of PROTONS in the nucleus of the atom of the element
Mass Number (A)
Total number of PROTONS and NEUTRONS in the nucleus
To determine the number of neutrons, simply subtract the atomic number from the mass number
(mass number — atomic number = # of neutrons)
Standard Atomic Notation
Mass number A Ion charge
X
Atomic number Z Subscript
(# of atoms in compound)
Structure of Atom
The atoms of each element are electrically neutral
→ in the neutral atom of any element, the # of protons = the # of electrons
→ electrons occupy the space surrounding the nucleus and are responsible for the chemical properties of the element
Dalton’s Atomic Theory of Matter
- All matter is made up of tiny particles called atoms. An atom cannot be created, destroyed or divided into smaller particles
- The atoms of one element cannot be converted into the atoms of another element
- All the atoms of one element share the same properties (mass and size). These properties are different for each element
- Atoms of different elements combine in specific proportions to form compounds
Modern Atomic Theory of Matter
- All matter is made up of tiny particles called atoms. Each atom is made up of smaller subatomic particles: protons, electrons, and neutrons
- The atoms of one element can be converted into the atoms of any other element by a chemical reaction called nuclear fusion
- All the atoms of one element share the same properties (mass and size). These properties are different for each element
- Atoms of different elements combine in specific proportions to form compounds
Ion
A positively or negatively charged particle that results from a neutral atom or group giving up or gaining electrons
Physical Properties
Description of matters
Qualitative Physical Properties
Describes the physical properties of a substance
EX: physical state, colour, odour, crystal shape, malleability, ductility, hardness, brittleness
Quantitative Properties
Involves measurement using accepted units
EX: melting point, boiling point, density, solubility, electrical conductivity, thermal conductivity
Chemical Properties
Properties of a substance we observe when matter is converted into different kinds of matter
Ex: reactivity with water, air, pure oxygen, acids, pure substances, combustibility (flammability), toxicity, decomposition
Physical State
The condition of being a solid, liquid, or a gas
Colour
Can be red, orange, yellow, green, etc.
Odour
Can be odourless, burnt, flowery, putrid, spicy, sharp, choking, nauseating, and suffocating
Taste
Can be sweet, sour, salty or bitter
Clarity
Can be transparent, translucent or opaque
Lustre
Ability of an object to reflect light
Form
Can be crystalline (regular cube shape) or amorphous (irregular shape)
Hardness
How easily the matter can be bent out of shape/ how easily it can be scratched
Texture
The feel of a substance can be fine, coarse, smooth, gritty, silky, fluffy, waxy…
Brittleness
The ability of an object to breakapart or shatter
Malleability
The ability of an object to be hammered into a sheet
Ductility
The ability of a substance to be stretched out into a long wire-like shape
Viscosity
Resistance of a liquid to flowing
Physical Change
No new substance is formed
Chemical Change
Causes at least 1 new substance, with new properties, to be formed
7 Pieces of Evidence of a Chemical Change
- Heat is produced or absorbed
- The starting material is used up
- A new colour appears
- A starting colour disappears
- A material with new properties forms
- Gas bubbles form in a liquid
- Grains of solid precipitate form in a liquid
Isotopes
Groups of atoms with the same atomic number but a different mass number
(Atoms with the same number of protons but a different number of neutrons)
Period
Horizontal rows containing elements
There are 7 Periods
Group / Family
Vertical columns containing elements with similar properties
There are 18 groups
Periodic law
When the elements are arranged in order of increasing atomic number, elements with similar properties occur at regular intervals
Group 1 (Alkali Metals)
Physical Properties:
Solid, shiny, soft
Chemical Properties:
Highly reactive, reactive with acid, lose e-
Group 2 (Alkaline Earth Metals)
Physical Properties:
Soft, shiny, solid
Chemical Properties:
Highly reactive, reactive with acid, lose e-
Group 17 (Halogens)
Physical Properties:
Solid, liquid, or gas, don’t conduct heat or electricity, low melting and boiling point
Chemical Properties:
Highly reactive, gain e-
Group 18 (Nobel Gases)
Physical Properties:
Odourless, colourless, tasteless,
Chemical Properties:
Low chemical reactivity, very stable, least reactive of all the elements
A duet has how many valence electrons?
An octet has how many valence electrons?
Duet→ 2 valence e-
Octet → 8 valence e-
Why is a neutral atom not stable but an ion stable?
A neutral atom is not stable because
the valence orbit is not completely full and does not follow the octet/duet rules. An ion is stable because it follows these rules.
Periodic Trends: Atomic Radius/Size
Family:
INCREASING atomic size down family due to adding orbits
Period:
DECREASING atomic size because of the greater attraction between p+ and valence e-
Periodic Trends: Ionization Energy
Family:
DECREASING ionization energy down the family due to the weakened attraction between p+ and valence e-
Period:
INCREASING ionization energy because atomic radius decreases across the period (more attraction between p+ and valence e-)
Periodic Trends: Electron Affinity
Family:
DECREASING electron affinity due to large atomic radius (weak attraction between p+ and valence e-)
Period: INCREASING electron affinity due to small atomic radius (greater attraction between p+ and valence e-)
Valence Electrons:
Outer electrons which are in the highest energy level
Electron Dot Symbols
Used to represent the atom and it’s valence electrons
Ionization
The process of changing an atom into an ion
Anion
An atom that gains electrons and is negatively charged
Cation
An atom that gives up an electron and is positive charged
Ionization Energy
The energy required to remove an electron completely from an atom
- expressed in terms of the energy required to remove electrons from a large quantity of atoms *
→ more energy to strip a small atom because the attraction is stronger
Electron Affinity
The energy given off when an electron is added to an atom
→ easier to add electrons to smaller atoms
Isoelectronic
Ion has the same number of e- to its nearest Nobel gas
EX. N3- is isoelectronic to Ne
Element
A pure substance that cannot be broken down into smaller particles by any ordinary means
Radioisotope
An unstable isotope that undergoes radioactive decay
What does it mean when electrons are in an excited state? Understanding this concept, what test can a chemist use to determine the identification of a metal?
When electrons are in an excited state, this means that it is in an energy state that is greater than the ground state it normally occupies. This happens when an electron absorbs energy and jumps to a higher orbital. Knowing this, a chemist can determine the identification of a metal by conducting flame test. The colour of the flame identifies the specific metal.
