Chemistry Ch. 4

a measure of how close a

measurement comes to the accepted or

true value of whatever is measured

Accuracy

is a measure of how close a series of measurements are to one another, irrespective of the accepted value.

precision

______________ Requires two or more repeated

measurements

precision

Darts on a dartboard illustrate the difference

between ___________ and __________

accuracy and precision

The closeness of a dart to the bull's-eye corresponds to

the degree of __________. The closeness of several darts to

one another corresponds to the degree of _____________.

accuracy

precision

the correct value for the

measurement based on reliable references

accepted value (theoretical, standard, actual, exact, true, published)

value measured in the lab

experimental Value

What is the equation for calculation % error?

I experimental - accepted I

% error = ---------------------------- x 100

accepted value

Measuring precision requires ____ or more

measured data points

2

What are the data points that measuring precision requires?

- Find the average of the

readings

- Determine the highest

measured value.

-Find the lowest measured

value

- Subtract the lowest value

from the highest.

- Report the range as the

precision

Sometimes you have bad data and the

_________ comes close to the _________ number. You

must look at the __________ so see how large of

swing there is.

average

accurate

precision

No, measurements are precise if they are easily

____________, but not accurate if they do not

reflect the ________ ______.

reproducible

accepted value

Who created the word atomos meaning atom?

domocratis

The number of protons in the nucleus of the atom.

atomic number

Usually from a Greek or

Latin word for the element or a substance containing the element.

element name

The average mass of the atoms in an element.

* Round this off to get the mass number

Atomic mass

Short-hand abbreviation for the element name.

symbol

What make up the nucleus?

protons and neutrons

________ and __________ are held together by a strong force.

protons and neutrons

The total number of

protons and neutrons in an atom (protons + neutrons)

mass number

The total number of

protons in an atom. (______ = protons)

atomic number

What makes one element different from another?

Elements are different because they contain different

numbers of protons (atomic number)

Atomic Number (periodic table) = _________

• # protons = __________ (if a neutral atom)

____________ = Atomic Number (protons) + Neutrons

• Neutrons = ________________________________

# protons

# electrons

Mass Number

Mass Number

Mass number - Atomic number

What makes an atom an ion?

if it looses or gains electrons and Electrons are not equal to the protons

What is a cation?

an atom with a positive charge (lost electrons):protons > electrons

what is an anion?

an atom with a negative charge (gain electrons):protons < electrons

atoms of the same

element that have equal

protons but different

numbers of neutrons

isotopes

If isotopes have the same protons, then they have the same _____________ number, but different ____________ number

atomic

mass

What is carbon 14 used for?

carbon dating

Isotopic signatures are commonly known as

______________, because they are similar to human

______________ and are used to track and trace.

- They are found in water, land, plants and

animals

fingerprints

fingerprints

All elements have ____________.

isotopes

of the 118 elements listed in the periodic table, only ___ occur naturally

94

What is democritus theory called?

Theory of the Universe

What is democritus key discovery?

First person to use the term atom

What is the word democritus came up with and what does it mean?

atomos: invisible

What was dalton's theory called?

Dalton's Atomic Theory

What was dalton's key discovery?

His atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties (atomic theory)

What were Dalton's for postulates?

1. All matter is made of atoms in are invisible

2. All atoms of a given element or identical in mass and properties

3. Compounds are combination of two or more different types of atoms

4. Chemical reaction is a rearrangement of atoms

Chemical reaction is a ___________________ of __________.

rearrangement of atoms

What was the problem with Dalton's model?

Atoms are not invisible. There are sub-atomic particles, electrons protons and neutrons.

What was the name of Thomson's model?

plum pudding

What was Thomsons key discovery?

He recognized electrons as components of atoms

What was the name of thomsons experiment?

Cathode Ray Tube

What is Thompson credited for discovering?

the electron

What did thomson's model look like?

blueberry muffin

(positive cake batter; negative blueberries)

What was the problem with Thompson's model?

There was no nucleus, and he didn't predict the movement of the electrons

What was the name of Rutherford's model?

nuclear model

What is the name of Rutherford's experiment?

gold foil experiment

What was Rutherford key discovery?

And prove there was a positively charged nucleus, because of deflection

Explain the Gold Foil Experiment.

Ernest Rutherford shot alpha particles at a sheet of gold foil and predicted that the particles would go through the sheet, but some of them refracted off. (because of the positive nucleus)

Who is the name of Bohr's model?

Planetary

What was Bohr's key discovery?

Electrons travel around the nucleus of an atom, in distinct circular orbits, or fixed energy levels

What was the name of Schrodinger's model?

Quantum mechanical

Did Schrodinger have an experiment?

No, he use math and quantum mechanics

What was Schrodinger's key discovery?

Electrons don't move around the nucleus in orbit, but in clouds wear their position is uncertain (quantum mechanical model)

What is special about Schrödinger's model?

It is still widely excepted at this is the most accurate model of the atom, and it is what we use today

What was the name of Chadwick's model?

He didn't have a model but rather inhanced, Schrodinger's quantum mechanical

What was Chadwicks key discovery?

neutrons

What makes up an atom nucleus?

neutrons and protons

How do you tell the percent abundance of an element?

The mass number that is closest to the mass number on the actual periodic table

How do you find the range of precision?

You calculate the highest number from the lowest number

How do you find the average?

You add all of the numbers up and then divide them by how many there are

How do you find precision and accuracy?

You're write the average number plus or minus the range of precision the average number is your accuracy compared to the true accepted number and you're a precision is the range of precision compared to 0.