atomic structure Flashcards
What are atoms?
Atoms are the smallest part of an element that can exist.
What do chemical symbols represent?
Chemical symbols represent an atom of an element.
How are compounds formed?
Compounds are formed from elements by chemical reactions.
What do chemical reactions involve?
Chemical reactions involve the formation of one or more new substances and often an energy change.
What do compounds contain?
Compounds contain two or more elements chemically combined in fixed proportions.
What is a mixture?
A mixture consists of two or more elements or compounds not chemically combined together.
How do the chemical properties of substances in a mixture compare to those in a compound?
The chemical properties of each substance in the mixture are unchanged, unlike in a compound.
How can mixtures be separated?
Mixtures can be separated by filtration, crystallisation, simple distillation, fractional distillation, and chromatography.
What was the first thought about the structure of atoms?
Atoms were thought to be tiny spheres that could not be divided.
How are elements arranged in the periodic table?
Elements are arranged in order of atomic (proton) number.
What is the significance of groups in the periodic table?
Elements with similar properties are found in the same columns, known as groups.
What do elements in the same periodic group have in common?
They have the same amount of electrons in their outer shell.
What model was proposed after the discovery of the electron?
The plum pudding model was proposed, where the atom is a ball of positive charge with negative electrons embedded in it.
What did the alpha particle scattering experiment conclude?
The experiment concluded that the mass of an atom was concentrated at the center (nucleus) and that the nucleus was charged.
Who ordered the periodic table by atomic weight?
John Newlands ordered his table by atomic weight.
What was the setup of the alpha particle scattering experiment?
A beam of alpha particles was aimed at very thin gold foil, and their passage through was detected.
What is the ‘law of octaves’ proposed by John Newlands?
Similar properties occur every eighth element.
What was observed during the alpha particle scattering experiment?
Some alpha particles emerged from the foil at different angles, and some even came straight back.
Why were the alpha particles deflected during the experiment?
The positively charged alpha particles were being repelled and deflected by a small concentration of positive charge in the atom (nucleus).
What limitation did Newlands’ periodic table have?
It broke down after calcium.
How did Mendeleev organize his periodic table?
Mendeleev ordered his table by atomic mass, but not always strictly.
Who suggested that electrons orbit the nucleus at specific distances?
Neil Bohr suggested that electrons orbit the nucleus at specific distances.
What did later experiments reveal about the nucleus?
Later experiments revealed that the positive charge of any nucleus could be subdivided into smaller particles, each having the same amount of positive charge (protons).
Why did Mendeleev leave gaps in his periodic table?
He left gaps for elements that he thought had not been discovered yet.
