Unit 1: Periodic Table, Matter, Chemical Trends Flashcards
Properties of Metals
Solid at room temperature
Except mercury
Good conductors of heat and electricity
Shiny
Ductile (can be stretched into thin wires)
Malleable (can be pounded into thin sheets)
A chemical property: contact with water results in corrosion
Properties of Nonmetals
Many are gases at room temperature (though some may be solid or liquid)
Poor conductors of heat and electricity
Dull
Not ductile or malleable. Solid nonmetals are brittle and break easily
Properties of Metalloids
Properties of both metals and nonmetals Solids Conducts better than nonmetals but not as good as metals Shiny or Dull Ductile & Malleable
Physical Properties
State Colour Texture Shape Clarity Solubility Temperature Density PH level
Physical Change
Change in state, size, shape, etc but the substance still stays the same
Chemical Change
a reaction, a new substance is formed
Chemical Property
Describes what a substance reacts with and the manner in which it reacts; describes what the substance is
Evidence of Chemical Change
Heat given off/cooling Light given off Precipitation Bubbles of gas Colour change Odour change
Qualitative Analysis
The identification of a chemical substance in a sample using physical and chemical properties
Quantitative Analysis:
The determination of how much of a given component is present in a sample
Isotope
Atoms of the same element with different number of neutrons
Radioisotope
Radioactive isotopes have the same chemical properties as stable isotopes of the same element, but they emit radiation, which can be detected.
Radioactive isotopes of an element with an unstable nucleus; it emits radiation as their nucleus decays (radioactive decay)
Types of Radiation
Alpha rays
Beta rays
Gamma rays
Alpha Rays
Symbol - Charge - Speed - Penetration in air - Effective Barrier - Composition -
Symbol - (α) Charge - Positively charged Speed - Slow Penetration in air - A few cm Effective Barrier - Tissue Composition - 2 p + 2 n (or helium, check pic)
Beta Rays
Symbol - Charge - Speed - Penetration in air - Effective Barrier - Composition -
Symbol - (β) Charge - Negative Speed - fast Penetration in air - A few m Effective Barrier - Aluminum Composition - 1 e (1 neutron is broken into 1 proton and 1 electron and that electron radiates off the of atom and makes the beta particle)
Gamma Rays
Symbol - Charge - Speed - Penetration in air - Effective Barrier - Composition -
Symbol - γ
Charge - Neutral
Speed - very fast
Penetration in air - unlimited
Effective Barrier - Lead plate (It can even penetrate through concrete of considerable thickness)
Composition - high-energy electromagnetic waves; Gamma rays are usually accompanied by alpha or beta rays
Half-Life
The time required for half of the original number of atoms in a radioactive sample to decay
But from after that, you just half the amount of atoms left
Half life = mass/2time/half-life
Uses of Radioisotope
Smoke Detectors Sterilizing Food and Equipment Radioactive Dating Radioactive Tracers Cancer Treatment
How much is one atomic mass (amu) and how much does each subatomic particle weight
1 amu = 1/12 of carbon-12 mass
1 p = 1 amu
1 n = 1 amu
1 e = 0.0005 amu
Average Atomic Mass and How To Calculate
Weighted average of all isotopes
AAM = (mass of isotope 1)(% available turned into decimals) + (mass of isotope 2)(% available turned into decimals)
Round to 2 decimal places and always put amu units
Periodic Law
The principle that physical and chemical properties of elements occur periodically when arranged by atomic number.
* A table best demonstrates these trends, so that similarities between elements appear in both rows and columns.
Periodic Trend
The relationship between atomic structure and physical/chemical properties Trends in Periodic Table: Atomic Radius Ionic Radius Reactivity (metal/non-metal) Ionization Energy Electron Affinity Electronegativity All of the trends depend on Force of Attraction (Fatt) between the valence electrons and the nucleus Fatt α Zeff/d^2
Atomic Radius
Higher force of attraction between valence electrons and atoms means smaller atomic radius
Lower Fatt means larger atomic radius
Atomic Radius - the radius of an atom
Half the distance between the neighbouring nuclei
measured in picometers (pm)
1pm = 10-12m
Effective Nuclear Charge (Zeff) and Number of Shells (d)
Effective Nuclear Charge (Zeff): Describes pull of nucleus on valence electrons (Net proton power)
Zeff = pull of the nucleus – shielding effect of inner electrons
Zeff = [number of protons] – [number of inner electrons]
Ex. Zeff for N is 7 – 2 = 5
*NOTE: Zeff will always equal the number of valence e- in an atom
Number of Shells (d) = period number
Ex. d = 2 for Nitrogen (2 shells)
Ionic Radius
The cations are smaller than their parent atoms because they have more protons than electrons, and also have 1 less shell, which increases Fatt.
The anions are larger than their parent atoms because they have a full valence shell and have more electrons than protons, which decreases Fatt.
The more positive an ion is the smaller it is because Fatt increases, while the more negative an ion, the larger it is because Fatt decreases.
Reactivity
An element’s ability to combine with other substances to become stable (isoelectronic to a noble gas – full outer shell)
Metals form positive ions by losing their valence electrons to obtain a noble gas configuration.
Their reactivity depends on how easily the metals lose their valence electrons.
Tend to lose e- to become stable
As Zeff ↑, Fatt ↑ (harder to lose e-) so Reactivity ↓
As d ↑, Fatt ↓ (easier to lose e-) so Reactivity ↑
Non-metals form negative ions by gaining valence electrons to obtain a noble gas configuration.
Their reactivity depends on how easily the non metals gain valence electrons.
Tend to gain e- to become stable
As Zeff ↑, Fatt ↑ (easier to gain e-) so Reactivity ↑
As d ↑, Fatt ↓ (harder to gain e-) so Reactivity↓
Ionization Energy
The minimum amount of energy required to remove the outermost electron from an atom or ion in the gaseous state.
Abbreviation is IEi, it has units of kJ/mol.
Low I.E. → gives electrons easily
High I.E. → does not give electrons easily
H (g) —-→ H + (g) + 1 e
Ionization energy goes higher as you go up a group on the periodic table and higher as you go right. (toward Fluorine basically)
Why does Ionization energy decreases down a group?
Fatt - weaker
less energy is required to remove an electron. I.E decreases.
Why does Ionization energy increases across a period?
Fatt - Increases
More energy is required to remove an electron (I.E increases)
Metals require lowest ionization energy because they have only 1-3 valence electrons, noble gases require most because of full valence shell
Electron Affinity
Energy change that occurs when an electron is added to an atom in the gaseous state.
UNITS: KJ/mol
Values are generally negative because energy is released.
Higher the negative number greater the electron affinity. I.e. easier for the element to gain an electron.
Think about it as an absolute value without the - to make it easier
The higher the number, the greater the electron affinity
Electronegativity
A measure of an atom’s ability to attract electrons into a chemical bond.
Pauling scale Fluorine 4.0 (most electronegative) - Francium 0.7 (least electronegative)
