Introduction Flashcards
Scientific notation set up?
Coefficient
Base: always ten when dealing with scientific notation
exponent
Decimal goes after the first non-zero digit
Why do we use scientific notation?
It’s easier and more convenient and helps express numbers with the right number of sig figs.
Why do we use sig figs? Precision? Accuracy?
We use sig figs to communicate the precision of our measurements
Precision: same thing again and again.
Accuracy: the correctness of your answer. Less sig figs leads to less accuracy.
Sig fig rules?
All non-zero digits are significant.
Zeros between sig figs are significant.
Other zeros are significant if they come after a decimal and after a sig fig.
Exact values have an infinite number of sig figs (counted items and defined values like how 100cm is equal to 1 meter like in dimensional analysis)
Sig figs when using operations?
The sun or difference must have the same number of decimal places as the least precise measurement.
The product or quotient must have the same number of sig figs as the least precise measurements.
Measuring with correct sig figs?
Analog devices are not digital and we have to read them. We estimate to one digit.
Look at the bottom of the meniscus curve.
For digital measuring tools just record what’s given.
What did Democritus do?
Democritus who lived in Greece during the fourth century suggested that matter was made of tiny particles that can’t be divided. He called these tiny particles atoms. He was the first to suggest the existence of atoms that were indivisible and indestructible.
However, his ideas weren’t useful in a scientific sense as they did not explain chemical behaviour and lacked experimental support because his approach was not based on the scientific method.
Dalton?
The modern process of discovery about atoms began with the theories of an English school teacher named John Dalton.
John Dalton’s Atomic theory?
All elements are composed of tiny indivisible particles called atoms.
Atoms of the same element are identical and made of the same atom, but differ from the atoms of another element.
Atoms of different elements can physically mix together, or can chemically combine in simple, whole number ratios to form compounds
Chemical reactions occur when atoms are separated, joined, or rearranged; however, atoms of one element are never changed into atoms of another element by a chemical reaction.
How is the atomic theory that is accepted today different from Daltons atomic theory?
Atoms now are known to be divisible. They can be broken down into smaller particles called subatomic particles like electrons, protons, and neutrons.
Terms of Jj Thompson experiment? Cathode ray tube
Anode: an electrode with a positive charge.
Cathode: an electrode with a negative charge.
Cathode ray: a glowing beam travelling between charged electrodes.
Electron: a negatively charged particle.
Why does production of cathode rays not depend on the kind of gas in the tube or the type of metal used for the electrodes?
Electrons must be part of the atoms of all elements.
Robert Millikan?What two properties of an electron did Robert Millikan determine from his experiments?
Was a US physicist
Wanted to find the quantity of charge carried by an electrons and found them from experiments.
Using charge to mass ration, he calculated the mass of an electrons.
Charge and mass
Electrons carry exactly one unit of negative charge.
It’s mass is 1/1840 the mass of a hydrogen atom.
What is true about atoms, matter, and electric charge.
Electric charges are carried by particles of matter.
Electric charged always exist in whole number multiples of a single basic unit.
When positively charged particles combine with an equal number of negatively charged particles, and electrically neutral particle is formed.
Positively charged subatomic particle
Proton
What charge does a neutron carry
None/zero
Why does an alpha particle have a double positive charge?
It’s a helium atom that lost two electrons
Rutherford experiment b
1911 shot a beam of alpha particles through a thin sheet of gold foil
A lot of the alpha particles passed through the gold atoms without deflecting
A small fraction bounced off at big angles. Some even bounces strait back toward the source.
Originally there should have been slight deflection due to the positive charge thought to be spread out.
What is true about the nuclear theory of atomic suggested by Rutherford experiment.
An atom is mostly empty space
All the positive charge of an atom is concentrated in a small central region called the nucleus.
The nucleus is small compared with the atom as a whole.
Nearly all the mass of an atom is in it’s nucleus.
Elements are diff because?
Their atoms contain diff numbers of protons.
What is atomic mass?
Weighted average
Isotopes
Diff formed of elements that are chemically alike because the have the same number of protons and electron, but a different number of neutrons.
Diff neutrons means diff mass numbers.
But protons and electrons are responsible for chemical behaviour and they have the same amount so they are chemically alike.
Different types of hydrogen?
Hydrogen 1- hydrogen
Hydrogen 2- deuterium
Hydrogen 3- tritium
Why is AMU used instead of grams to express mass number.
In grams the number is too inconveniently small and impractical to work with. It’s more useful to compare the relative masses of atoms using a reference isotope as a standard.
