Chem CH 2&4

Significant figures in mathematical operations

- multiplication and division problem: number of sig figs in result is the same as the number w the least amount of sig figs -for addition and subtraction problems: the limiting term is the number with the least amount of decimal places (the result will have that many places after the decimal as the least number w least amt)

the elements

-118 known (88 naturally) -only 9 elements in earths crust (diff from living matter)

Rules for Counting Significant Figures

-Nonzero integers always count as sig figs. -Leading zeros never count as sig figs. -Captive zeros always count as sig figs. -Trailing zeros only count as sig figs if the number is written with a decimal point. "100" has 1 sig fig. "100." has 3 sig figs. -Exact numbers (numbers that were determined by counting and not through measuring devices) can be assumed to have an unlimited number of sig figs. Therefore, exact numbers never limit the number of sig figs when it is used in a calculation.

how is the term Element used

-could be a single atom -Couldmeanmoleculesofanelement(H2) -Ciuld mean atoms of allowed are found in some form

Dalton's Atomic Theory

1) elements are composed of atoms. 2) atoms of same element are identical, but differ from other elements. 3) elements can mix together to form compounds 4) atoms only change when mixed with other elements

Fundamental SI Units

1000m= 1km 0.1m(10^-1)=0.1 dm 0.01m(10^-2)=1cm 0.001m(10^-3)=1mm 0.0000001m(10^-6)=1micrometer 0.0000000001m(10^-9)=1nm 1mL=1cm3 1L=1dm3 1kg=2.2046 1lb=453.59g

Law of Constant Composition

A given compound always contains elements in exactly the same proportion by mass

pure substance

A sample of matter, either a single element or a single compound, that has definite chemical and physical properties

quantitative observation

An observation that deals with a number or amount Unit tells scale

Isotopes

Atom w same number of protons but diff number of neutrons is tickle him popertoe bc of eectrpns

Draw x a and z

Atomin number mass and element

why is high density lipoprotein good?

Bc it has a lower volume thus takes up less space in body

Why Do ifferent atom bc diff chem properties

Bc of electrons

Metalloids

Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, PoloniumSilicon (Si) Germanium (Ge) Arsenic (As) Antimony (Sb) Tellurium (Te)

Compound

Distinct substance that is composedof atoms of two or more elements and always contains exactly the same relative masses of those elements (2 atoms of h for every 1 o in water)

Physical properties of metals

Heat and eectrocit malleabilty ductility wire lustrous

Temperature conversion equations

K = C+273 C = K-273 F = 1.80(C)+32 C = (F-32)/1.80

groups on periodic table

List

A given pair of elements might combine to form

More than one compound

Rutherford and chadwik

Most nuclei contain neutron beautiful is lightly more massiv than proton by no charge

18 most abundant elements

Oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium, hydrogen, titanium, chlorine, phosphorus, manganese, carbon, sulfur, barium, nitrogen, fluorine

Ernest Rutherford

Plum pudding is wrong arom has a sense center of positive charge o repel the charges articles of alpha Electrons travel around nuclear proton ha same magnitude of charge as lctron but is positive ss

William Thomson s

Plum pudding model plum itself is positive but has little negative beerries

JJ Thomson

Showed that atoms can be made to emit tiny negative particles concluded that atoms must also have positive charges to balance out negative

Measuring the volume of a solid object by water displacement

You find the volume of the object by subtracting the difference in water as it rose (amt of water before -amt of water after) = volume of object

diatomic molecule

a molecule that consists of two atoms of the same element so reactive they bind to themselves i bring clay for our new home

qualitative observation

deals with descriptions that cannot be expressed in numbers

Allotropes

different molecular structures of the same element Solid carbon diamond graphite buckminsterfullerene

ionic compound

metal and nonmetal combine High melting point Conduct electricity if melted and in water transfer of electrons neitral-sum =0

Physical properties of non metals

more variation in properry lack prop of metald can be gases l or a at room temp

Ions

positively and negatively charged atoms atoms can form ion by gaining or losing electrons metals tend to lose electrons to form positive cations ( magnesium cation) nonmetals tend to gain electrons to form negative anions ( sodium chloride)

Mass

the amount of matter in an object