C1 Flashcards
(14 cards)
What did John Dalton propose about atoms?
John Dalton described atoms as solid spheres. He suggested that different types of spheres might make up different elements.
This was proposed in the early 1800s.
What model did J.J. Thomson propose in 1897?
J.J. Thomson proposed the plum pudding model, suggesting that atoms cannot be solid spheres and must contain negatively charged particles (electrons).
He described the atom as a general ball of positive charge with discrete electrons stuck in it.
What experiment did Ernest Rutherford conduct in 1909?
Ernest Rutherford fired positively charged alpha particles at a sheet of gold to investigate the atomic structure.
He expected the alpha particles to pass through if the positive charge was spread out.
What unexpected result did Rutherford observe in his experiment?
Some alpha particles were deflected to the side, and a small number were reflected back, indicating a problem with the existing atomic model.
This led Rutherford to propose a nuclear model of the atom.
What did Rutherford’s nuclear model propose?
Rutherford’s nuclear model proposed that instead of a general positive charge, there was a compact nucleus containing all the positive charge of the atom, with negative charge existing in a cloud around it.
What did Niels Bohr suggest in 1913?
Niels Bohr suggested that electrons orbited the nucleus and were held in shells. The orbiting of the electrons prevents the atom from collapsing.
Who provided evidence for neutrons?
James Chadwick provided evidence for neutral particles in the nucleus, known as neutrons.
Who composed the modern periodic table?
Dimitri Mendelev composed the periodic table around the mid 19th century.
What did Mendelev predict during the construction of the periodic table?
Mendelev predicted that there would be new elements that had not yet been discovered.
How are elements arranged in the periodic table?
Elements are arranged in increasing atomic number, which represents the number of protons or electrons in that element.
What pattern did Mendelev find in the elements?
Mendelev found that the elements displayed a pattern of chemical properties. Every time a pattern repeated, he formed a new line called a period.
What do elements in the same group have in common?
Elements in each group have similar chemical properties because they have the same number of electrons in their outer shell.
What is true about Group 1 elements?
Group 1 elements, known as alkali metals, all react violently with water and become more reactive as you go down the group.
What is true about Group 7 elements?
Group 7 elements, known as halogens, become less reactive as you go down the group.
