Atomic structure Flashcards
What was John Dalton’s model of atomic structure in the early 1800s?
Atoms were thought to be tiny, hard spheres that could not be divided. Each chemical element had its own atoms differing in mass. Atoms rearranged in chemical reactions.
Dalton’s model laid the foundation for modern atomic theory but was later revised as new discoveries were made.
What significant discovery did J.J. Thompson make in the 1890s?
The discovery of the electron.
Thompson used high voltages applied to gases at low pressure to discover negatively charged particles.
What model did J.J. Thompson propose for atomic structure?
The plum pudding model.
This model depicted an overall sphere of positive charge with negatively charged electrons embedded within it.
What was the main conclusion from Geiger and Marsden alpha particle scattering experiment in 1911?
The atom is mainly empty space with mass concentrated in a positively charged nucleus.
This experiment involved shooting alpha particles at a thin sheet of gold foil.
What did Niels Bohr propose about electron behavior in 1914?
Electrons orbit the nucleus at specific distances, forming shells with fixed energy levels.
Bohr’s model adapted the nuclear model and was confirmed by experimental observations.
Fill in the blank: Before the discovery of the electron, atoms were thought to be _______.
tiny, hard spheres.
True or False: The plum pudding model proposed by J.J. Thompson depicted atoms as having a dense nucleus.
False.
The plum pudding model suggested a diffuse distribution of positive charge, unlike the concentrated nucleus in the nuclear model.
What phenomenon led Rutherford to conclude that the nucleus is positively charged?
The deflection of alpha particles in the scattering experiment.
The majority of alpha particles passed through gold foil, but a few were deflected, indicating a dense, positively charged center.
What was a key feature of Bohr’s atomic model?
Specific energy levels for electron orbits.
This was a significant advancement from previous models, aligning with experimental data.
What is the smallest piece of an element that can still be recognised as that element?
Atom
Atoms are the fundamental building blocks of matter.
Define an element.
A substance that consists of only one type of atom
Elements cannot be broken down into simpler substances by chemical means.
What is a molecule?
Two or more atoms covalently bonded together
Molecules contain a fixed ratio of atoms.
What particles make up an atom?
- Proton
- Neutron
- Electron
These are the fundamental subatomic particles of an atom.
What is the relative charge of a proton?
+1
Protons carry a positive charge.
What is the relative charge of a neutron?
Neutral, no charge 0
Neutrons do not carry any electrical charge.
