Chapter 5 Test Flashcards
What is a physical property and some examples of it?
- Description of the substance that does NOT involve the formation of a new substance
- A charactertsic or description of substance
- Ex. color, texture, density, smell, solubility, taste, melting point, and physical state
- IT CAN BE REVERSED while some cannot
- Dissolving sugar in water can easily be reversed through evaporation but cutting a log cannot be reversed
What is a chemical property and some example of it?
- Description of what a substance does and its ability as it changes into 1 or more NEW substances
- Ex. a new color appears, heat or light is produced, bubbles of gas are formed, a precipitate (insoluble solid) is formed
- DIFFICULT TO REVERSE
- Recharging batteries reverses the substances back to their original chemicals
Is boiling water a chemical change?
boiling water is not a chemical change, it is a change of state so a physical change
Simply a change of arrangement of molecules but the substance still has remained the same
What is a physical change? Give some examples.
- Where a substance remains the same substance but changes its physical properties in some way
- Ex. salt dissolves in water, steel wool turned the black pot a shiny silvery color, spilled gasoline dried but left a bad odour in the room, the paint on your car dulled, a tire is inflated with air
What is a chemical change and give some examples?
- A substance changes into one or more different substances
- Ex. milk sours, pancakes cook on a griddle, the back steps are rotting out, cavity in your tooth
Name 4 things that classify as a chemical reaction and examples with it.
- The reaction of an acid with a base (vinegar reacts with baking soda to produce carbon dioxide gas
- Flammability (gasoline burns when lighted)
- Bleaching ability (hydrogen peroxide breaks down the pigment in hair)
- Corrosion (batteries in landfill slides break down when they come in contact with groundwater)
What is the difference between physical change and physical property?
Anything that can be measured without changing the identity or chemical composition of the substance is known as the physical property of a substance. A physical change involves the formation of a new arrangement of matter but the structure of the atoms and molecules remains the same
What is the difference between chemical change and chemical property?
Chemical properties are useful in identifying substances, but can only be observed as the substance is in the process of being changed into a different substance. A chemical change, also known as a chemical reaction, is a process that occurs when one or more substances are changed into one or more new substances.
What is an element?
pure substance that cannot be broken down into simpler substances
What is the periodic table?
a structural arrangement of elements that helps us to explain and predict physical and chemical properties (this is why different elements in different locations react differently than any other element)
What are periods?
- Horizontal rows on periodic table
- All elements in a row have the same number of electron shells.
What are groups and which groups are contained within them, explain their charcateristics.
- Vertical columns on periodic table
- Elements in the same column have similar physical and chemical properties
- Group 1: Alkali metals
Not include hydrogen
Soft, highly reactive metals because only 1 valence electron
React with water - Group 2: Alkaline earth metals
Light, reactive metals - Group 17: Halogens
Highly reactive - Group 18: Noble gases
Most stable (outer orbits are full), rarely reactive
What do elements that have similar valence electrons have in common?
The similar number of valence electrons results in elements within a group having similar chemical reactivity.
List some properties have metals.
State at room temp: solid
Lustre: shiny
Malleability: generally malleable
Electrical conductivity: conductor
Why do metals only give up their electrons?
Metals have a low electron affinity (a less likely chance to gain electrons) because they want to give up their valence electrons rather than gain electrons, which require more energy than necessary.
List some properties of non-metals.
State at room temp: solid, liquid, gas
Lustre: dull
Malleability: brittle (if solid)
Electrical conductivity: insulator
List the subatomic particles.
Proton: +1 charge, 1 amu, nucleus location
Electron: -1 charge, 1 amu, orbit around nucleus
Neutron : 0 charge, 1/2000 amu, nucleus location
Why are atoms neutral?
→ Atoms have no charge where there is a SAME amount of protons and electrons where their charges cancel out
Why are ions charged?
→ Charged atoms (Ions) where # of protons does NOT equal # of electrons so a charge forms
What is the standard atomic notation?
Standard atomic notation = international standard of conveying info of an element
Ex. 16 8 0 ← 16 is the atomic mass and 8 is atomic # for Oxygen
What are valence electrons and what are they responsible for?
- The particles on the outermost shell of atom that are involved in bonding
- The outer electrons are responsible for the element’s reactivity
What are the rules with Bohr-Rutherford?
–>First orbit: 2 max
→ Second orbit: 8 max
→ Third orbit: 18 max but 8 is when it is stable
2-8-8 rule applies to first 20 elements mostly
What is the formula to determine energy levels?
→ Formula to determine energy levels: 2n^2 where n is the shell #
What does the stability of the group 18 explain?
→ The stability of group 18’s outer shell helps explain why elements combine to form compounds (meaning: two or more elements in a fixed ratio)
What are isotopes?
→ All neutral atoms of the same element have the same # of protons and electrons but the # of neutrons can vary
→ Isotopes: atoms of an element that have the same # of protons but different numbers of neutrons that VARY
→ Many elements have TWO or more naturally occurring stable isotopes
→ The average atomic mass (found on periodic table) is is used to determine the atomic mass of an element that has more than one isotope which have different masses
→ Isotopes are found in different ABUNDANCES so weighted average takes into account how much of each type of isotope there is for a particular atom
-The atomic mass is an average of an element’s atomic masses, weighted by the natural abundance of each isotope of that element. It is a weighted average because different isotopes have different masses.
What is isotopic abundance?
→ Isotopic abundance: the amount of a given isotope of an element that exists in nature, expressed as a PERCENTAGE of the total amount of this element
Example 1: Find average atomic mass of copper:
Copper-63 62.93 amu 69.2% abundance
Copper-65 64.93 amu 30.8% abundance
Formula for average atomic mass:
[mass of isotope 1 x abundance] + [mass of isotope 2 x abundance]
= [62.93(0.692)] + [64.93(0.308)]
= 43.54756 + 19.99844
= 63.546
= 63.55 amu
Example 2: Calculate the isotopic abundance of each isotope of Boron:
Boron-10 10.01 amu x%
Boron-11 11.01 amu x%
10.81 = [10.01(x)] + [11.01(1 - x)] ← let x rep abundance of boron-10 and (1-x) abundance of 11
10.81 = 10.81x + 11.01 - 11.01x
10.81 = 11.01 - x
-0.2 = -x
0.2 = x
0.2 → 20% → for Boron-10
Boron-11:
100% - 20% = 80%
Example 4: Argon has three naturally occurring isotopes: argon-36, argon-38, and argon-40. Based on argon’s reported atomic mass, which isotope exists as the most abundant in nature? Explain.
Argon has an atomic mass of 39.948 amu, which is closest to argon-40, suggesting that it is the most abundant isotope.
What happens to the trends after the first 20 elements?
They have different rules
What is atomic radius?
the distance from the centre of an atom to the approximate boundary of their electron cloud
What happens across a period with atomic raduis and why? give example
→ Across a period: DECREASES because electrons are added to the same energy level and one proton is added for each electron. This increases the positive charge inside the nucleus which pulls the electrons in closer, decreasing the atom’s size
Ex. Li → large atomic size because it has a less effective nuclear charge than F which has a small atomic radius
What is effective nuclear charge?
Effective nuclear charge: ability of nucleus to attract electrons
What happens down a group with atomic radius and why?
→ Down a group: INCREASES because the electrons are placed in higher energy levels which are further from the atom’s nucleus which increases the atom’s size
What is ionization energy?
the amount of energy required to remove a valence shell electron from an atomW
What happens across a period with ionization energy and why? give example
→ Across a period: INCREASES because the increased positive charge in the nucleus increases the attraction between the nucleus and electrons, making the electrons more difficult to remove
Ex. Li has less nuclear charge so less energy needed to take electrons away while F has a strong nuclear charge so more energy is required
What happens down a group with ionization energy and why?
→ Down a group: DECREASES because electrons are further away from the nucleus and the attraction between electrons and the nucleus is weaker, making th electrons easier to remove
What is electron affinity?
opposite of ionization energy, measure energy change that occurs when an electron is added to outer shell of an atom to form negative ion, larger the change in energy, the higher the electron affinity, a measure of how much an atom wants to add an electron to their valence shell
What happens across a period with electron affinity and why? give example
→ Across a period: INCREASES because the number of valence electrons increases so the closer an atom as a full outer shell, the higher its affinity for another electron to join
Ex. F has a greater electron affinity because it is better at attracting electrons as it has a stronger nuclear charge than Li
What happens down a group with electron affinity and why?
→ Down a group: DECREASES slightly because valence shell electrons are further away from positively charged nucleus so they will have a less affinity for electrons
- A lower electron affinity indicates that an atom does not accept electrons as easily because they want to give them up instead
- A trend of decreasing electron affinity going down the groups in the periodic table is because the additional electron will be entering in an orbital farther away from the nucleus. Since this electron is far from the nucleus it experiences less attraction towards the nucleus and would release less energy when added.
What is electronegativity?
a measure of the ability of an atom to attract electrons, higher the number, the better the atom is at attracting an electron
What happens across a period with electronegativity and why?
→ Across a period: INCREASES because the number of valence electrons increases so the closer a full outer shell, the more it will attract electrons to fill it up
What happens down a group with electronegativity and why? give example
→ Down a group: DECREASES slightly because valence shell electrons are further away from positively charged nucleus so they will have a less ability to attract electrons
Ex. Li would better attract electrons than Na
What is an atom?
Atom: electrically neutral particle with an equal number of electrons and protons
What is an ion?
Ion: atoms that has become charged by GAINING or LOSING one or more electrons
What is a stable octet?
Stable octet: 8 valence electrons
What is a cation and anion?
Cation: positively charged ion (+1 charge and loses one electron)
Anion: negatively charged ion (-1 charge and gains one electron)
What are rules with ionic compounds?
→ Name of positive ion is same as name of element (Na = sodium, Na+ = sodium)
→ Name of negative ion adds “ide” to name of element (F = fluorine, F- = fluoride)
→ Metals LOSE electrons and become CATIONS
→ Non-metals GAIN electrons and become ANIONS
What does it mean for an atom to become isoelectronic?
→ Atoms become isoelectronic (means the same # of electrons) to a noble gas
Ex. Na become isoelectronic to Ne (Na has 11e → lose 1e → 10e and Ne has 10e)
What are some patterns with ions in the periodic table?
→ Across a period: values increase by 1 up to +3 and then increase by -1 from -3
→ Down a group: all elements have the same ionic charge
→ Group 14 have 4 valence electrons so they are likely to lose or gain electrons so they don’t have a fixed charge
→ Group 18 is already stable
Why are ion compounds neutral?
→ Sum of the charges on the positive ions equal the sum of teh charges on the negative ions
What does the chemical formula describe about the ionic compound?
→ A chemical formula describes a compound using elements symbols and numbers which indicate the number of atoms of each element found in the compound (METALS IS FIRST and NON-METAL IS SECOND)
Ex. AgI → silver iodide
Explain the interaction of ionic compounds and water.
→ Some ionic compounds are soluble in water, where they separate into ions where water molecules surround each ion as it leaves the crystal which prevents the ions from rejoining the crystal
→ Water is a universal solvent
→ Ionic bonds are very strong, the water is more attracted to chemicals, cuaisng it to break its bond
Explain some properties of ionic compounds.
→ Ionic compounds are hard, brittle solids with high melting points
→ Most ionic compounds are electrolytes that carry a current and dissolve into water to produce a solution that conducts electricity
What is a compound?
A compound is substance made up of different elements joined together by a chemical bond.
What is IUPAC?
- International Union of Pure and Applied Chemistry
- Decides how we name elements
What are elements with multiple ion charges?= and how do we name them?
→ Some metals can form more than one kind of ion
→ When naming, first determine the charge of the metal and then indicate it by a ROMAN NUMERAL in brackets after the metal in the name (find the ionic charge on periodic table)
Ex. CuCl → Cu has 2+ or 1+ and Cl has 1-
x + (-1) = 0
x = 1
Copper (I) chloride
What is a polyatomic ion?
- Ions made up of more than one atom that acts as a single particle.
- The ionic charge of a polyatomic ion is shared over the entire atom
- Polyatomic ions are ions.
- Covalent bonds, on the other hand, hold the atoms in polyatomic ions together.
- Ionic chemicals are those that include polyatomic ions.
How do you name polyatomic ions and what is the order?
→ When naming an ionic compound with a polyatomic ion, the CATION (usually metal) is named FIRST, followed by the polyatomic ion.
→ The rules for multivalent metals still hold true for these ionic compounds
Ex. Mg(ClO3)2 → magnesium chlorate
Co(No3)2 → cobalt (II) nitrate
How do you write formulas for polyatomic ions and what is the rule?
→ Use brackets around the polyatomic ion if the ionic charge on the cation is greater than 1
Ex. Calcium phosphate
Ca and PO4
Ca2+ and (PO4)3- ← PUT BRACKETS HERE
Ca3(PO4)2
Ammonium sulfate (BOTH POLYATOMIC)
NH4 and SO4
(NH4)+ and (SO4)2-
(NH4)2 and SO4 ← bracket is taken off because the charge is only 1
(NH4)2SO4 → subscripts of 2 and 4 are not simplified because they are both polyatomic particles and cannot be simplified as those 4 charge is a part of them
What is a molecular substance and what contains within the chemical formula?
A pure substance formed from two or more non-metals. The chemical formula of a molecular compound give the exact number of atoms in each molecule
What happens when two non metals are with each other and how does this form a covalent bond?
→ When two nonmetals bond with each other, both nuclei strongly attract the other’s electrons. This results in a tug of war for electrons that neither atom ever wins. The net effect is that two atoms share each other’s electrons, forming a covalent bond. The bonded atoms form a molecule
What are diamtomic molecules?
→ Molecules that consist of two atoms joined with a covalent bond are called diatomic molecules (Diatomic molecules are normally composed of elements that have a space for one more electron in its valence shell. As a result, two atoms of the element can create a covalent bond, hence sharing an electron each, and providing one another with a full valence shell)
What is a polar bond and a non-polar bond?
Polar and non-polar refers to the level in which two elements equally share a pair of electrons. Individual bonds can be polar or nonpolar, as can entire molecules. Polar means there is unequal sharing of electrons, while nonpolar means equal sharing.
Why do we use electronegativites for polar and non-polar bonds?
Using electronegativities, we can predict the type of bond that will occur between two atoms → basically to determine if sharing in covalent bond is equal or not
What do you do when the bond is polar?
Use the symbol negative delta to indicate the atom with the higher electronegativity and use the symbol positive delta to indicate the atom with the lower electronegativity
What are the rules with naming molecular compounds?
→ Use a prefix to indicate the number of each element present
→ **If there is only one atom of the first element, the prefix is not used
→ The order of the elements in the name is the same as in formula
→ The ending of second element needs to change to -ide
→ DO NOT REDUCE FOR MOLECULAR COMPOUNDS
Ex.
N20 → dinitrogen monoxide
Carbon tetrachloride → CCl4
Can an element undergo chemical change?
An element is a substance that can not be broken down into simpler substances. This does not mean that it can not undergo chemical changes. Elements chemically react with other elements to form a variety of compounds.
Compare the chemical and physical properties of non-metals and metals
Metals tend to be hard, shiny, malleable, ductile, and good conductors, while nonmetals are more varied in their physical properties, but are generally poor conductors. Chemically, metals tend to lose electrons and react easily while nonmetals are more likely to gain electrons and form covalent bonds.Wh
What are some characterstics of a substance that could be discovered by studying its chemcial properties
The change of one type of matter into another type (or the inability to change) is a chemical property. Examples of chemical properties include flammability, toxicity, acidity, reactivity (many types), and heat of combustion.
What is a molecular compound and what do covalent bonds do?
Molecular Compounds- Definition. Molecular compounds are compounds held together by covalent bonds. Molecular compounds are compounds formed from two or more nonmetallic elements. Covalent bonds hold atoms of different elements together in molecules in a molecular compound.
Difference between molecules and compounds
A molecule is a group of two or more atoms held together by chemical bonds. A compound is a substance which is formed by two or more different types of elements which are united chemically in a fixed proportion. All molecules are not compounds. All compounds are molecules.
A molecule is a group of two or more atoms bonded together, while a compound is a type of molecule that contains different elements.
molecules are two or more atoms chemically bonded and a compound is two or more elements chemically bonded.
Compare ionic compounds and molecular compounds properties.
Properties of Ionic Compounds
- High melting points.
- High boiling points.
- A crystal lattice structure.
- Solids break easily into sheets.
- Solids do not conduct electricity and are good insulators. (Ionic compounds are conductors of electricity when molten or in solution, and insulators when solid.)
- ionic bond
- electrostatic attraction
Molecular compounds
Covalent compounds are low melting and boiling points, low heat of vaporization, low solubility in water, and poor conductors of electricity and heat.
- covalent bond
- sharing of electrons
