Chapter 2 Flashcards
The ancien Greeks believed that there were __#__ elements. Give the number of element and state them.
4 earth fire water air
Who proposed the concept of atoms?
Democritus and Leucippos
What lead to the discovery of many elements and important chemicals like minerals acids?
Alchemy : For about 2000 years people attempts to transmute “base” metals (the cheap ones) in to gold.
What is the Dalton’s atomic theory? (6 answers)
- Each element is made up of tiny particles called atoms
- The atoms of a given element are identical
- Chemical compounds are formed when atoms combine with each other.
- A given compound always has the same relative numbers and types of atoms
- Chemical reactions involve reorganization of that atoms – changes in the way they are combined.
- The atoms themselves are not changed in a chemical reaction
What was Dalton’s mistake in classifying atomic masses?
he assumed that the formula of water was HO, so he introduced many errors in his list of atomic masses where he was out by a factor of 2.
Who recognized the static electricity?
Benjamin Franklin
Who discovered that uranium gave off invisible radiation that could fog a piece of photographic film through black paper?
Henri Becquerel
Who first isolated radium and polonium in 1898 and what the person suggest?
Marie Curie
She suggested they were emitting this radiation as the elements decayed to form other elements
The radiation can be analysed and shown to contain 3 components. What are these components?
Alpha particles (α) Beta particles (β) Gamma rays (γ)
The properties of electron were established by two main experiments. The first one was held by J.J. Thomson. What was his experiment?
Cathode Rays: the charge on the plates and the magnetic field strength were adjusted so that the electron beam did not deviate from a straight line. Some relatively simple calculations enable Thomson to calculate the ration of the charge to the mass of the electron
The properties of electron were established by two main experiments. The second one was held by Millikan. What he established and how he established it?
He established the charge and mass of the electron.
Millikan measured the charge on a number of oil drops and took the smallest difference as the charge on the electron
e= -1.60 X 10^ -19 c
Who designed an experiment to probe the interior of an atom?
Ernest Rutherford
How Ernest Rutherford designed an experiment to probe the interior of an atom?
A bean of a particles was directed at a thin gold foil to investigate how it would be scattered.
What are the properties of subatomic particles ?
for the answer see: https://lh3.googleusercontent.com/-Ehum7bfQQno/VMtXXFTTUpI/AAAAAAAABZQ/Zcjg_CSANQo/w800-h800/p-n-e-data.jpg
Atoms are made of
- Electrically _______ protons
- Electrically _______ electrons
- Electrically _______ neutrons
Negative, neutral or positive
protons: positive
electrons: negative
neutrons: neutral
What surround the nucleus
the electrons
The number of __________ is equal to the number of protons.
electrons
The atomic number gives_______________
the number of protons in the nucleus
What is the atomic mass unit (u) ?
one atomic mass unit = 1/12 of the mass of an atom of carbon with 6 protons and 6 neutrons
What information gives the mass number?
the sum of the number of protons and neutrons of an atom
What is a cation?
It’s an atom that losses an electron or electrons and it becomes positively charged
what is an anion?
It’s an atom that gains an electron or electrons and it becomes negatively charged
What is an isotope?
it’s atoms with the same atomic number but different mass number
Isotope: all atoms of the element have the same number of ____________
protons
