Flashcards in C1: Atomic Structure And The Periodic Table Deck (36):
What is an atom?
An atom is the smallest part of an element that can exist
What are all substances made out of?
What are atoms of elements represented by?
All atoms are represented by a chemical symbol eg O for oxygen and Na for sodium
About how many different element are there and where are they shown?
About 100 and in the periodic table
How are compounds formed?
Formed from elements by chemical reactions
What do chemical reactions always involve?
The formation of one of more new substances and often a detectable energy change
What do compounds contain?
Two or more chemically combined elements in fixed proportions
How are compounds represented?
By using a formulae that uses the symbols of the atoms from which it was formed
How can compounds be separated?
By chemical reactions
How can chemical reactions be represented?
By word equations or symbol/formulae equations
What does a mixture consist of?
Two or more elements that are not chemically combined together
How are mixtures separated?
Through physical processes such as filtration, crystallization, fractional distillation, simple distillation and chromatography
Before the discovery of the electron, what were atoms thought to be?
Tiny spheres that can't be divided
What did the discovery of the electron lead to?
The plum pudding model of the atom
What did the plum pudding suggest?
It suggests that the atom is a ball of postive charge with negative electrons
What did the results from the alpha particle model lead to?
It led to the plum pudding model being replaced with the nuclear model which includes the atom with a charged nucleus in the middle of it and the mass of the atom was concentrated there
What's different about the nuclear model?
It includes the atom with a charged nucleus in the middle of it and the mass of the atom was concentrated there
What did Niel Bohr do?
He adapted the nuclear model by suggesting that the electrons orbit around the nucleus at specific distances
Was Bohr's suggestion accepted?
Yes because experimental observations agreed with his theoretical calculations
What did later experiments lead to?
It led to the idea that the positive charge of the nucleus could be subdivided into smaller particles which each had an equal amount of positive charge,
these were called protons
What did James Chadwick do?
His experimental work led to the discovery of neutrons 20 years after the idea of the nuclear model was established
What's the relative electrical charge of a Proton?
What's the relative electrical charge of a Neutron?
What's the relative electrical charge of an Electron?
What's the overall electric charge of an atom?
There is none
How small are atoms?
They are very small
They have a radius of 0.1nm
How small is the nucleus?
The radius is less than 1/10000 of an atom's radius
What are the relative masses of a Proton, neutron, and electron?
Electron: very small
What do elements in the same group in the periodic table have in common?
They have the same number of electrons in their outer shell
How are elements in the periodic table arranged?
They're arranged by atomic (proton) number
How did scientists classify elements before the discovery of protons, neutrons, and electrons?
By atomic weights
What were the early periodic tables like?
Incomplete and some elements were placed in inappropriate groups
What did Mendeleev do?
He left gaps for elements he thought hadn't been discovered and in some places changed the order
What did knowledge of isotopes do?
They made it possible to understand why the order based on atomic weights wasn't always correct
Elements that react to form positive ions are