Chem Review Flashcards
Elemental Composition of Human Body
Hydrogen= 63% Oxygen= 24.2% Carbon= 10.5% Nitrogen=1.35% Major Minerals=0.7% Trace Elements= 0.01%
Dalton’s Theory of the Atom
All matter is composed of atoms that can be neither created nor destroyed.
Atoms of a particular element are identical in size, shape, mass and all other properties and differ from atoms of other elements in these properties.
Atom
Element in its smallest form
Molecule
Two or more atoms combined (bound)
The atoms may be same element or different elements
Atomic weight
Similar to mass
Relative masses of atoms are related to the most abundant carbon isotope, Carbon 12, and differ widely in masses.
Why is the weight of carbon listed as slightly higher than 12 sometimes?
Because of the existence of some carbon isotopes in nature, Carbon 13 for example
Neutron
No charge (0) Amu= 1.0087
Proton
Positive Charge +
Amu=1.0078
Electrons
Negative charge -
Amu= .00055
Most distinguishing characteristic of an element?
The number of protons, or positively charged particles in the nucleus of an atom.
If you lose a proton, you will have a different element
Mass of an element is composed of?
Protons and neutrons
Electrons are very small are hardly contribute to the mass (atomic weight)
Atomic Nucleus
Atoms have a small concentrated positive charge in the atomic nucleus
What occupies the surrounding space around the nuclear atom?
Most of the atom is space and electrons occupy this surrounding space.
Nucleus has a positive charge and electrons has a negative charge and these will be attracted to each other
How much space do electrons and protons take up in atom?
Nucleus takes up a very small amount of the atom=protons
Electrons circulation around the nucleus take up the most space
The Neutral Atom
Number of electrons=number of protons
Z number of an element
Represents Atomic number
Number of protons
If element is neutral, then protons and electrons are equal
How are atoms presented on the periodic table?
In their neutral form, although they are not neutral in the environment. This is just an easier way to study them
Can two elements ever have the same number of protons?
NO, that’s the distinguishing factor
In the periodic table how are elements arranged?
According to atomic number
General notation of elements. What does A, E and Z represent?
A= mass (protons+neutrons)
E=element by identity symbol
Z=atomic number (number of protons)
As we move down the periodic table what do we see?
As we move across what do we see?
We see similar properties of elements in columns as we move down
We see different properties as we move across?
Isotopes
Some atomic masses differ for same atom
Isotopes that have the same atomic number, but different atomic masses.
In isotopes, the atomic nucleus of a given element has a fixed number of protons, but the neutrons vary
Not all isotopes are radioactive
Hydrogen vs. Deuterium (2H)?
Hydrogen has 1 proton and 0 neutrons= atomic mass of 1
Deuterium has 1 proton and 1 neutron= atomic mass of 2
Inert or noble gases properties
VIIIA (far right of periodic table)
Helium, Argon, Krypton, Xenon, Radon
Properties: do not react, all gases at normal temperature
Alkali or light metals
IA, except H- Far left of table
Lithium, Sodium, Potassium, Rubidium, Cesium, Francium
Properties: in pure form have shiny lust, good conduction of heat and electricity
Halogens
Group VII A
Fluorine, Chlorine, Bromine, Idoine
Properties: no metals, poor conductors of heat and electricity, all react with hydrogen to form hydrogen halide. Ex: hydrogen fluoride, hydrogen chloride
Transition Metals
IIIB-IIB can have variable charges
Row 3 of table- Magnesium, Sulfur.
A decrease in metallic properties is seen.
Atomic Radii of elements
Increase in atomic radii from top to bottom of periodic table
The effect of ionization in atomic radii
The addition of electrons has a major effect on atomic size
The addition or removal of a single electron roughly increases or decrease the radii by half.
Ionized
Gaining or losing an electron
Electronegativity
The ability of an atom to draw (attract) electrons or a negative charge towards it.
Electronegativity is not ionization.
Values are relative, note that fluorine has the highest value of 4.0
Electronegativity increases left to right, and decreases from top to bottom.
Why do elements at the bottom of the periodic table has decreased Electronegativity?
When a neutral atom has more protons, it has more electrons.
Electrons shield that nucleus and have less interaction with the protons.
More electrons=more shielding=less Electronegativity
Ionization
Energy required to ionize an element
Inert elements have the highest ionization energies– most difficult to ionize
Easiest to ionize= Li, Na, K, Rb, Cs
Nuclear Stability
Nucleus is packed tightly with positive particles and would seem to want to fly apart
Neutrals act to stabilize the nucleus
In order to achieve stability, the more protons in a nucleus- there needs to be more neutrons.
Ionization energy is a periodic property of elements
Which elements hard to ionize?
Which elements easier to ionize?
Hard to ionize or require the most energy to ionize is Helium.
Inert elements are hard to ionize, they have 8 electrons in outer shell and do not like to lose this electron
Easiest to ionize= Alkali metals, Lithium, Sodium, Potassium
Usually give up on electron and become positively charged
When the neutron-to-proton ratio is too high or too low what happens?
Too high or too low= nuclear stability is altered leading to radioactive processes.
Radioactive processes
Occurs when nuclei are trying to achieve stability
This process changes the number of neutrons or protons to try to reach stability.
When this occurs they release energy in a form of radioactive particles
Beta particle
An electron, or -1 charge that is released during radioactive decay process
Alpha particle
Associated w/ heavier elements normally
Alpha particle= two protons and two neutrons (+2 charge)
Gamma rays
(Y)= no mass or charge, but high energy particles (photons)
When radioactive decay occurs does the element change?
YES
Sometimes number of protons is changed. Example: tritium in notes
As elements get larger, what happens to neutron-to-proton ratio?
As element gets larger, they are less stable because there are more protons, and nucleus gets bigger. It then is harder to hold this element together.
Neutrons are thought to play a role in stabilizing the protons and keeping them together