Atoms and Subatomic Atoms and Subatomic ParticlesParticles

How big is an atom?How big is an atom?

►An atom is incredibly smallAn atom is incredibly small The diameter of an atom would have to be The diameter of an atom would have to be

increased 200 million times to have the increased 200 million times to have the diameter of a pennydiameter of a penny

If an apple were enlarged to the size of If an apple were enlarged to the size of the Earth, the atoms in the apple would the Earth, the atoms in the apple would be the size of cherriesbe the size of cherries

What is an atom made of?What is an atom made of?

► Subatomic particles: Subatomic particles: Neutron, proton, electronsNeutron, proton, electrons A central, dense nucleus A central, dense nucleus

(neutrons & protons) (neutrons & protons) surrounded by electronssurrounded by electrons►Electrons have a negative Electrons have a negative

charge (-)charge (-)►Protons have a positive Protons have a positive

charge (+)charge (+)►Atom is held together by the Atom is held together by the

attraction of electrons and prattraction of electrons and protonsotons

►Neutrons are neutralNeutrons are neutral

electron

neutron

proton

How much does an atom weigh?How much does an atom weigh?(What is it’s mass?)(What is it’s mass?)

►Atoms are so small that it is Atoms are so small that it is impractical to use grams impractical to use grams 1 atom1 atom ͌ ͌ 1010-23-23 g g

► Instead atoms are measured in atomic Instead atoms are measured in atomic mass units or amu’smass units or amu’s One carbon atom is 12.0 amu’s and all One carbon atom is 12.0 amu’s and all

atoms are compared to thisatoms are compared to this

Particle Mass (kg) Mass (amu) Charge

Electron 9.10939 x 10-31 0.00055 -1

Proton 1.67262 x 10-27 1.00728 +1

Neutron 1.67262 x 10-27 1.00728 0

Most of the mass in an atom is in the nucleus

Subatomic Particles

ATOMIC FACTSATOMIC FACTS

► Most of the mass of an atom is in the nucleus: the protons and neutrons

► The size of the neutron relative to the size of the atoms is like a penny in the middle of a baseball field

► The number of protons and electrons need to be equal so that the atom has no charge

ATOMIC NUMBERATOMIC NUMBER

►The number of protons in the nucleus The number of protons in the nucleus of an atomof an atom Atomic numbers of naturally occurring Atomic numbers of naturally occurring

elements:elements:►Lowest=Hydrogen (H)Lowest=Hydrogen (H)

Z=1Z=1

►Highest=Uranium (U)Highest=Uranium (U) Z=92Z=92

►Periodic Table of ElementsPeriodic Table of Elements

ATOMIC NUMBERATOMIC NUMBER

Remember, Remember,

The number of protons in the nucleus of The number of protons in the nucleus of an atom equal the number electrons so,an atom equal the number electrons so,►Atomic number=Atomic number=►Number of protons=Number of protons=►Number of electronsNumber of electrons

Mass NumberMass Number

►Sum of the number of protons and the Sum of the number of protons and the number of neutrons in the nucleus of number of neutrons in the nucleus of the atom:the atom: Mass number=# of protons + # of Mass number=# of protons + # of

neutronsneutrons And…..And…..

►Mass number=atomic number + # of neutronsMass number=atomic number + # of neutrons►# of neutrons=mass number – atomic number# of neutrons=mass number – atomic number

IsotopesIsotopes

►Atoms of an element that have the same Atoms of an element that have the same number of protons and electrons but number of protons and electrons but different numbers of neutrons.different numbers of neutrons. Hydrogen isotopesHydrogen isotopes

►Hydrogen has 1 proton, 1 electron and 0 neutronsHydrogen has 1 proton, 1 electron and 0 neutrons►Deuterium has 1 proton, 1 electron and 1 neutronDeuterium has 1 proton, 1 electron and 1 neutron

Therefore, it is heavier than hydrogen but has similar Therefore, it is heavier than hydrogen but has similar chemical properties and slightly different physical chemical properties and slightly different physical propertiesproperties

►Tritium has 1 proton, 1 electron and 2 neutronsTritium has 1 proton, 1 electron and 2 neutrons

Atomic MassesAtomic Masses► Atomic massAtomic mass ͌ ͌ Mass numberMass number

They are close but not the sameThey are close but not the same► Here’s whyHere’s why

1.1. Mass number is an exact number & atomic mass Mass number is an exact number & atomic mass is a weight so it’s an inexact numberis a weight so it’s an inexact number► Hydrogen has a mass number of 1 (1 protron + 0 Hydrogen has a mass number of 1 (1 protron + 0

neutrons),neutrons),► But weighs: But weighs: 1.00728 amu

2. Atomic masses are calculated based on the percentage of isotopes present in natural world

H=99.985%; D=.015%; T=trace Atomic mass of H is: 1.00794 Periodic table of elements

Chemical Basis of LifeChemical Basis of Life

►Most common elements in living Most common elements in living organismsorganisms Carbon (C): 9.5%Carbon (C): 9.5% Hydrogen (H): 63%Hydrogen (H): 63% Oxygen (O): 25.5%Oxygen (O): 25.5% Nitrogen (N): 1.4%Nitrogen (N): 1.4%

MacromineralsMacrominerals

►Minerals we need a lot ofMinerals we need a lot of Calcium (Calcium (CaCa)) Phosphorous (Phosphorous (PP)) Magnesium (Magnesium (MgMg)) Potassium (Potassium (KK)) Sodium (Sodium (NaNa))

MicromineralsMicrominerals

►Needed in small quantitiesNeeded in small quantities Iron (Iron (FeFe)) Copper (Copper (CuCu)) Chromium (Chromium (CrCr)) Fluoride (Fluoride (FF)) Iodine (Iodine (II)) Selenium (Selenium (SeSe)) Molybdenum (Molybdenum (MoMo)) Zinc (Zinc (ZnZn))