where alchemy became chemitry Flashcards
Who proposed the idea of the atom in ancient Greece?
Democritus
Democritus proposed that matter is made up of tiny, indivisible particles called atoms.
What is the meaning of the Greek word ‘atomos’?
‘uncuttable’
The term refers to the indivisible nature of atoms as proposed by Democritus.
What are the key points of Dalton’s Atomic Theory?
- All matter is made of atoms.
- Atoms of the same element are identical.
- Atoms of different elements are different.
- Atoms combine in simple whole-number ratios.
- Atoms are rearranged in chemical reactions but are not created or destroyed.
What did J.J. Thomson discover in 1897?
The electron
J.J. Thomson discovered the electron using a cathode ray tube experiment.
What model did J.J. Thomson propose?
Plum Pudding Model
The model suggested that atoms are spheres of positive charge with negatively charged electrons embedded inside.
What did Rutherford’s gold foil experiment reveal?
Atoms have a small, dense nucleus
Rutherford’s experiment showed that most of the atom is empty space with a nucleus containing positively charged protons.
What is the Bohr Model known for?
Electrons exist in specific energy levels
Niels Bohr proposed that electrons can jump between energy levels by absorbing or emitting energy.
What concept did the Quantum Mechanical Model introduce?
Probability clouds for electrons
This model states that electrons exist in probability clouds rather than specific orbits.
Who created the first widely recognized periodic table?
Dmitri Mendeleev
Mendeleev arranged elements by increasing atomic mass and left gaps for undiscovered elements.
What did Henry Moseley discover about the arrangement of elements?
Elements should be arranged by atomic number
Moseley’s work led to the modern periodic table based on the number of protons.
What are the two main arrangements in the modern periodic table?
- Periods (horizontal rows)
- Groups (vertical columns)
What defines the atomic number of an element?
The number of protons in the nucleus
What is the mass number of an atom?
The total number of protons and neutrons in the nucleus
What are isotopes?
Atoms of the same element with different numbers of neutrons
What does the Periodic Law state?
The properties of elements are periodic functions of their atomic numbers
Fill in the blank: Groups contain elements with similar properties due to the same number of _______.
valence electrons
Fill in the blank: Periods represent elements with increasing _______.
atomic numbers
True or False: The periodic table is a fundamental tool in chemistry.
True
What was a significant breakthrough in organizing elements in the periodic table?
Mendeleev’s periodic table
Mendeleev’s arrangement and predictions for undiscovered elements were crucial for the development of chemistry.
What did the quantum mechanical model explain?
The behavior of subatomic particles
