CHEM1400 Chapters 1-3

What is chemistry

Often called the central science, the study of matter and the changes it undergoes with direct applications to many other fields of study

Biomolecules

DNA, RNA, proteins

Scientific laws

a concise verbal and or mathematical statement that describes a reliable relationship between phenomena

ex) ideal gas law

Scientific theory

explains a body of experiential observations and laws

ex) the kinetic theory of gases

SI base units

systems international; common modern form of the metric system

Weight

a force exerted by gravity on an object

Mass

a measure of the amount of matter regardless of the gravitational field

Atomic mass unit

AMU or Dalton Da

1.6605378×10^-24g=1amu=1Da

Accuracy

tells how close a series of measurement is to the true value

Percision

tells how close a series of measurements are to one another

Pure substances

form of matter that has a specific chemical composition and distinct properties, state, and solubility (water, iron, salt, oxygen)

mixtures of substances

ex) salt water and brass(combo of copper and zinc)

States of matter

solids, liquids, gases, plasma (more common)

Plasma

most common source of matter, ionized(charged) matter, doesn’t have well-defined boundary/shape but highly electrically conductive (the sun)

Homogenous mixture

uniform composition

Heterogeneous mixture

not uniform compesition

Physical state and properties of matter

melting point, color, observed

chemical properties of matter

observed when a chemical change of chemical processes happens to matter and pure substances/mixture no longer exists

extensive properties

ex) volume, mass, length

depends on amount of matter

These properties change as the quantity of matter changes, meaning they are additive; the total value is the sum of the values of the individual parts

Intensive properties

don’t depend on the amount of matter there

ex) temperature, density, color, solubility

It is a bulk property, meaning it is not dependent on the size or mass of a sample.

When dividing 2 extensive properties together

you get an intensive property

Atoms

they are the building blocks of matter, smallest units of matter that still retain the properties of that matter

Elements

term related to atoms; the substance can’t be broken down into 2 or more substances by any means

Carbon

C

14

Backbone of organic and biological molecules

Hydrogen

H

1

Most abundant element in universe; organic and biological chemistry

Oxygen

O

16

Basis of aerobic respiration, organic and biological chemistry

Nitrogen

N

15

Constituent of amino acids, proteins, nucleic acids

Sulfur

S

16

Important in metabolism including extremophiles

Sodium

Na

1

Important for nerve impulses, muscular function

Potassium

K

1

Similar to Na, important for nerve impulses and muscular function

Calcium

Ca

2

Bone formation; geology

Fluorine

F

17

One of the most reactive elements

Chlorine

Cl

17

Physiology, water balance in cells, digestion

Bromine

Br

17

animal life, collagen form

Iodine

I

17

metabolism, thyroid hormones

Silicone

Si

14

Semiconductor, important in modern electronics

Iron

Fe

8

steel, hemoglobin

Copper

Cu

11

cofactor for enzymes

helium

He

18

2nd most abundant; nuclear fusion

Thompson 1899

discovered the electron, first discovered subatomic particle

Millikin 1909

determined the charge of an electron by suspending charged oil drops in an electric field

Rutherford 1917

proposed the nucleus was a structure confined to a small region of space. Positive charged alpha particles → shot them at a thin foil like gold. Sometimes alpha particles went through sometimes not

Most atoms space is empty, there is a nucleus, nucleus is positively charged

Chadwick 1920

discovered neutrons

Atomic number

denoted by Z, number of protons

#of electrons=#of protons

Ion

When number of protons doesn’t equal the amount of electrons

Mass number

denoted by A, number of protons(Z) + neutrons (N)

Mass # A is superscript

Atomic # Z is subscript

Are the number of protons (Z) fixed for a given element?

Yes, the number of protons for an element are fixed

Isotopes

atoms with the same Z (Atomic #) but different A (Mass #)

Do the number of protons and electrons play a bigger role in chemical properties?

Yes the number of protons and electrons play a big role in chemical properties

Coulombic force

an electromagnetic force and same charged particles repel each other

Strong nuclear force

extremely short-range force at lengths on the scale of the size of the diameter of the proton it’s about 100x stronger than the coulombic force

Weak nuclear force/interaction

force inside the nucleus, interconversion of protons and neutrons and important for nuclear fusion

When are isotopes reactive?

All isotopes arising from elements with Z greater than or equal to 82 are radioactive

Magic numbers

associated with stable nuclei, all even numbers

radioactive decay

involves emission of particles and or electromagnetic radiation from the nucleus

Alpha particles

the nucleus of helium without electrons

Beta particles

an electron that arises from the nucleus when neutrons convert to protons by the weak interaction. Often leaves the nucleus at relativistic speeds

Gamma rays

true electromagnetic radiation, release for many nuclear processes

Columns of periodic table

groups/families, share similar chemical and physical properties

Horizontal rows of the periodic table

the first period just has hydrogen, H and helium, He

Most elements are what?

Most elements are metals and good conductors of heat and electricity

Are nonmetals good conductors?

Non, nonmetals are not good conductors

Metalloids

between nonmetals and metals in terms of properties and include elements like silicone

Group 1

alkali metals

Group 2

Alkali earth metals- alkaline

Group 3 to 11, sometimes 12

Transition metals/ transition elements D block

Group 17

the halogens

Group 18

The Noble gases, don’t react much

Other groups on the periodic table are called what?

Other groups are simply called by the name of the uppermost element of the group

ex) 13 is called Boron group/family

2 rows underneath the main periodic table

F-block elements

1 mole particle=

6.0221413×10²³ of those particles (Avogadro’s number)

Molar mass

mass of grams of a substance in 1 mole

S block

Left side of the periodic table

D block

Middle of the periodic table

P block

Right side of the periodic table past the diagonal line

metals

nonmetals

metalloids

Group 1 and 2 throw off what easier?

They throw off electrons easier

Energy

The ability to do work/transfer of heat

Kinetic energy

Ek energy of motion, associated with the mass of the moving object(m) and its speed(u)

Can have the units joules, kilojoules, J/mol, KJ/mol, electronvolts(eV), calories(cal), or nutritional calories(Cal)

Potential energy

associated with the position of an object in a field

Electrostatic(potential) energy

Eel the potential energy and object (like an ion) experiences in an electric field. Charged particles of the opposite sign attract and the same sign repulse each other

Q is charge

d is the distance between the charged particle when Eel is positive is repulsive, Eel is negative is attractive

Law of conservation of energy

Energy is not created nor destroyed, but different forms of energy can interconvert

Joules, Kilojoules, KJ/mol, J/mol

don’t forget to convert g ←→kg

1000g=1kg

Energy (J) is directly related to?

Force(N-newtons) J=NxM work =forcexdistance

Electromagnetic spectrum

EM light is just a region of spectrum

The energy of EM radiation is transferred as waves(wavelength, frequency, and amplitude)

Visible light

400nm (violet) to 700nm(red) based on average human perception of light, ROYGBIV

Wavelength

Distance between identical points meters(m), nanometers (nm), picometers(pm)

10^-9m=1m

1pm=0.001nm

Frequency

number of waves that pass through a defined point per unit time (1sec)

1Hz=1/s

short wavelength-high frequency

long wavelength- low frequency

Amplitude

the vertical line from the midline to the top of the crest/bottom of the trough

The frequency and wavelength of EM waves is related by the following:

C= speed of light in a vacuum 2.9979×10^8m/s

Electric field

EM waves have up/down waves

Magnetic field

EM waves have perpendicular out/in waves

Constructive interference

EM waves can have same 2 frequencies/wavelength/amplitude that leads to one larger wave

Destructive interference

EM waves can have 2 different frequencies/wavelengths/amplitudes that leads to one flat line

Quantum theory

how matter and energy behaves at the smallest scale vs bigger scale

Quantization of energy

Problem in science that was trying to explain blackbody radiation- EM radiation emitted from heated objects (sun, glowing swords)

Blackbody radiation

when an object is cooler, it gives off most of its energy as longer wavelengths (infrared). When an object is hotter, the max of the curve shifts to shorter wavelengths toward visible (light of even UV)

hotter=bluer

A hotter object doesn’t just change color it gives off more total energy

What is a blackbody?

An ideal object that absorbs all light that hits it and then re-emits energy as light when its hot. The light it gives off depends only on its temperature (T) intensity of radiation vs wavelength

Planck distribution law

He was able to model the blackbody radiation behavior incorporating a parameter h

h=6.626×10^-35 Js

Oscillations inside the heated material had discrete modes, not a continuum of values—and the EM radiation coming off the blackbody was emitted in discrete amounts. This is one of the earliest proposals of quantization of energy in a material

Photoelectric effect

metal exposed to light of under a certain threshold wavelength or frequency did not eject electrons form the surface (ex photoelectrons)

above that threshold, photoelectrons were ejected and increased in numbers in direct proportion to the intensity of light

photoelectron energy=Light energy in - binding energy

W is work

Bohr’s theory of the hydrogen atom

sun and other objects that emit white light that forms its emission spectrum, this white light is a combo of colored light. Pure elements like H show the atomic line spectra- the EM radiation emitted is specific wavelengths and is characteristic of that element

Rydberg constant

1.09737316×10^7 m^-1