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Atomic Structure
Cards in this deck (8)
- 1Atomic Structures Ideas of atoms have changed over timeJohn Dalton published his ideas about atoms in 1803. He thought that all matter was made of tiny particles called atoms, which he imagined as tiny spheres that could not be divided.
J J Thomson carried out experiments and discovered the electron. The atom is a ball of positive charge with negative electrons embedded in it, it is known as the Plum Pudding. - 2In 1909, Ernest Rutherford designed an experiment to test the plum pudding model. In the experiment, positively charged alpha particles were fired at thin gold foil. Most of the particles went straight through the foil. But a few were scattered in different directions.Rutherford to suggest a new model for the atom, called the nuclear model. In the nuclear model:
The mass of an atom is concentrated at its centre, the nucleus
The nucleus is positively charged - 3Niels Bohr adapted Ernest Rutherford's nuclear model. Bohr did calculations that led him to suggest that electrons orbit the nucleus in shells.Each proton has a small amount of positive charge.
James Chadwick found evidence for the existence of particles in the nucleus with mass but no charge. These particles are called neutrons. - 4Nucleus and Shells An atom has a central nucleus. The radius of an atom is about 0.1 nm (1 × 10-10 m) The radius of a nucleus (1 × 10-14 m) is less than frac{1}{10,000} of the radius of an atomSubatomic particles
The nuclei of all atoms contain subatomic particles called protons. The nuclei of most atoms also contain neutrons.
The masses of subatomic particles are very tiny. - 5Atomic Numbers REMEMBER: All atoms of a given element have the same number of protons Atoms of different elements have different numbers of protonsAn atom contains equal numbers of protons and electrons. Since protons and electrons have equal and opposite charges, meaning that atoms are have no overall electrical charge.
- 6Mass Numbers Atoms of different elements usually have different mass numbers, but they can be the same. E.G: the mass number of argon atoms and calcium atoms can both be 40.Calculating numbers of subatomic particles
The Mass is written at the top and the atomic number is written at the bottom. - 7Isotopes Atoms of the same element with different numbers of neutrons are called isotopes. Isotopes have an element of: Same Atomic Number Different Mass numberRelative Atomic Mass
Relative atomic masses can be found in the periodic table. They have the symbol Ar.
REMEMBER:
Mass numbers are always whole numbers
Relative atomic masses are always rounded to the nearest whole numbers - 8Electronic Structure An electronic structure is the way in which electrons are arranged in an atom. Electrons in atoms occupy energy levels, also called electron shells, outside the nucleus.ELECTRONIC STRUCTURE FOR Sodium
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- need help on three isotopes of hydrogen calculating relative atomic mass
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