chapter 2 chem

element

pure substance that cannot be broken down into simpler substances by a chemical reaction

how many elements known - how many naturally occurring and how many prepared by scientists

118 known, 90 naturally occurring, 28 prepared by scientists in lab

elements in periodic tabel are divided into what

3 categories: metals, nonmetals, metalloids

periodic table always on ALEKS!!!

metals

shiny materials that are good conductors of heat and electricity

• all metals are solids at room temperatire except for mercury, which is a liquid

nonmetals

• do not have a shiny appearance

• generally poor heat and electricity conductors

  • non metals like sulfur and carbon are solids at rom temp; bromine is a liquid, nitrogen, oxygen and nine other elements are gases

metalloids

• properties intermediate between metals and nonmetals

building block elements

• 4 nonmetals - CHON are 96% of human body mass

major elements or macronutrients

• present in the body in much smaller amounts (0.1-2% by mass)

other elements in body

• sodium, potassium, and chlorine are present in body fluids

• Mg + S in proteins

• Ca + P in teeth + bones

• P in all nucleic acids e.g. DNA that transfers genetic info from 1 gen to another

• at least 100mg of each macronutrient needed

trace elements / micronutrients needed in diet in

smalll quantities, usually less than 15 mg

-each one has specialised func important for proper cell func.

compound

pure substance formed by chemically combining 2 or more elements tgt

common element colors for molecular art

red sphere is

oxygen

white - grayish sphere is

hydrogen

darkish grey sphere is

carbon

blue sphere is

nitrogen

light green sphere is

fluorine

darkish green sphere is

chlorine

brown sphere is

bromine

purple sphere is

iodine

s is

sulfur

p is

phosphorus

all matter is composed of the smae basic building blocks called….

atoms

3 subatomic partices of atom

• proton - p - pos charge

• electron - e- - neg charge

• neutron - n - no charge

nucleus

dense core that contains the protons and neutrons

• contains most of the mass of an atom

electron cloud

composed of electrons that move rapidly in the almost empty space surrounding the nucleus

• compromises most of the atom’s volume

opposite charges —-

attract

like charges

repel each other

diag opp charge and like charge

atomic mass unit

• defines the mass of individual atoms relative to standard mass

atomic number (Z)

number of protons in the nucleus - every atom of a given type of element always has the same number of protons in the nucleus

• in a neutral atom, cuz it has no overall charge, atomic number (Z) = no. of protons or electrons (in the electron cloud) in the (neutral) atom

how is the periodic table arranged

in order of increasing atomic number beginning at the upper left hand corner

mass number

number of protons + number of neutrons

“(A)

how to find number of neutrons

= subtract atomic number from mass number

e.g. 40 - 18 = 22

isotope

• atoms of the same element having a different number of neutrons

e.g. of isotope

all atoms of chlorine have 17 protons in nucleus, but some chlorine atoms have 18 neutrons in teh nucleus + some have 20 neutrons in nucleus

isotope symbol

• cuz all chlorine ayoms have same atomic number (17), it is sometikes omitted - so chlorine with mass number of 35 can be written as ^(35)Cl and (^37) Cl

hydrogen isotopes

mass number weighs down atomic number in isotope symbols!!

mass number weighs… (IN ISOTOPE SYMBOL!!)

down the atomic number