Atoms and Elements Flashcards

Elements

pure substances from which all things are built
cannot be broken down into simpler substances
certain elements look alike and behave in the same way

Chemical Symbols

one or two letter abbreviations for the names of the elements
only the first letter is capitalized
if two letters are capitalized... represents the symbols of two different elements

Mercury (Hg)

a silvery, shiny element
liquid at room temperature
can enter the body:
- inhaled mercury vapor
- contact with the skin
- ingestion of foods and water contaminated with mercury
effect on body:
- destroys proteins and disrupts cell function
- can damage the brain and kidneys
- can cause mental retardation
- can decrease physical development

Periodic Table

organizes 118 elements into groups with similar properties
places them in order of increasing atomic mass

Periods (periodic table)

horizontal rows of elements
counted from top to bottom of the table
Periods 1 to 7

Groups (periodic table)

vertical columns
contains elements with similar properties

Group Number (periodic table)

written at the top of each vertical column
uses A for representative elements or B for transition elements

Representative Elements (periodic table)

uses the letter A
(Groups 1A - 8A)

Transition Elements (periodic table)

uses the letter B
in center of periodic table
(Groups 3B - 12B)

Alkali Metals (Group 1A)

elements are:
- soft
- shiny
- good conductors of heat and electricity
- have relatively low melting points
- react vigorously with water
- form white products when they combine with oxygen
includes:
- Li (Lithium)
- Na (Sodium)
- K (Potassium)
- Rb (Rubidium)
- Cs (Cesium)
- Fr (Francium)

Alkaline Earth Metals (Group 2A)

includes:
- Be (Beryllium)
- Mg (Magnesium)
- Ca (Calcium)
- Sr (Strontium)
- Ba (Barium)
- Ra (Radium)
elements are:
- shiny
- not as reactive as alkali metals

Halogens (Group 7A)

includes:
- F (Fluorine)
- Cl (Chlorine)
- Br (Bromine)
- I (Iodine)
- At (Astatine)
elements are:
- highly reactive
- form compounds with most of the elements

Noble Gases (Group 8A)

includes:
- He (Helium)
- Ne (Neon)
- Ar (Argon)
- Kr (Krypton)
- Xe (Xenon)
- Rn (Radon)
elements are:
- quite unreactive
- seldom found in combination with other elements

Metals Nonmetals, and Metalloids

separated by heavy zigzag line
metals... to the left
nonmetals... to the right
metalloids... along the heavy zigzag line

Metals

located to the left of zigzag
shiny solids
can be shaped into wires (ductile)
can be hammered into a flat sheet (malleable)
good conductors of heat
substances that loses electrons very easily
usually melt at higher temperatures than nonmetals
all metals are solids at room temperature except mercury

Nonmetals

located to the right of zigzag
dull
brittle
poor conductors of heat and electricity
low densities
low melting points

Metalloids

located along zigzag
better conductors than nonmetals but not as good as metals
semiconductors, because they can be modified to function as conductors or insulators

Elements Essential to Health

20 elements essential for the well-being and survival of the human body
Four elements -- Oxygen, carbon, hydrogen, and nitrogen make up 96% of our body mass
Macro minerals-- Ca, P, K, CL, S, Na, and Mg
- are representative elements involved in the formation of bones and teeth, maintenance of heart and blood vessels, muscle contractions, nerve impulses, acid-base balance of bodily fluids
- Regulation of cellular metabolism

Atom

all elements on the periodic table are made up of atoms
the smallest particle of an element that retains the characteristics of that element
consists of a nucleus that contains protons and neutron
Electrons are in a large empty space around the nucleus
Protons are inside the nucleus
Neutrons are also inside the nucleus

Dalton's Atomic Theory

All matter is made up of tiny particles call atoms
All atoms of a given element are similar to one another and different from atoms of other elements
Atoms of two or more different elements combine to form compounds
A chemical reaction involves the rearrangement, separation, or combination of the atoms. Atoms are never created or destroyed during a chemical reaction

Electrical Charges in an Atom

Atoms contain subatomic particles:
- Protons
  - have a positive charge
  - Much heavier than the electrons
  - Inside of the nucleus
  - Is attracted to an electron
  - one proton has a mass of 1.67 x 10^-24 g
- Electrons
  - have a negative charge
  - much smaller than the atom
  - have extremely small masses
  - In a large empty space around the nucleus
  - Repel each other
  - one electron has a mass of 9.11 x 10^-28g
- Neutrons
  - are neutral
  - Inside the nucleus

Determination of the Mass of an Atom

The masses of the protons and neutrons in the nucleus determine the mass of an atom

Atomic Mass Unit

¹/₁₂th of the mass of a carbon atom which has a nucleus contains six protons and six neutrons
A proton has a mass of about 1 (1.007) amu
A neutron has mass of about 1 (1.008) amu
An electron has a very small mass, 0.000549 amu

Atomic number

is a whole number specific for each element
Is the same for all atoms of an element
Is equal to the number of protons in and atom
appears above the symbol of an element in the periodic table
The number of electrons is also equal to the atomic number

Atom is electrically neutral

The number of protons in and atom is equal to the number of electrons which gives every Adam and overall charge of zero

Mass Number

Is the total number of protons and neutrons in the nucleus
Does not appear on the periodic table
Mass number = number of protons + number of neutrons
represents the number of particles in the nucleus
Always a whole number

Isotopes

atoms of the same element that have the same atomic number but different numbers of neutrons
Have the same number of protons but different numbers of neutrons
Can be distinguished by their atomic symbols

Atomic symbol

The mass number in the upper left corner
The atomic number in the lower left corner

Atomic Mass

A weighted average of all the naturally occurring isotopes of an element
the number including decimals that is given below the symbol of each element

Energy Levels

Assigned principal quantum numbers
Electrons in the lower energy levels are closer to the nucleus
While electrons in the higher energy levels are farther away from the nucleus
The energy of an electron is quantized… It can only have specific energy values
All the electrons of the same energy are grouped in the same energy level
The higher energy levels are closer together
The lower electron energy levels hold fewer electrons in a higher energy levels

Changes in electron energy level

Electrons move to higher energy levels when they absorb energy
When electrons fall back to lower energy level, light is emitted
the energy emitted or absorbed is equal to the differences between the two energy levels

Electron Arrangement

Gives the number of electrons in each and Energy level

Valence Electrons

The number electrons in the outermost energy level
The group number gives the number of valance electrons for each of the representative elements

Electron dot symbol

Also known as Lewis structures
Represents the valance electrons as dots place on the sides of a symbol

Atomic size

Is determined by the atom's atomic radius, the distance between the nucleus and outermost electrons
Increases for representative elements from top to bottom of the periodic table
Decreases with within a period As a result of the increased number of protons in the nucleus

Chemistry: Atoms and Elements Flashcards