Döbereiner grouped the known elements into <em>triads</em> (sets of three) so that
• The <em>atomic mass of the middle element</em> was approximately the average of the other two
• The <em>chemical properties of the middle element</em> were between those of the other two
• The <em>physical properties of the middle element</em> were between those of the other two
One example of a triad is Li – Na – K.
(a) Atomic mass of Na = 23.0 u
Average atomic mass of Li and K = (6.9 u + 39.1 u)/2 = 46.0 u/2 = 23.0 u
(b) Li reacts slowly with water. Na reacts rapidly. Potassium reacts violently.
(c) Melting point of Na = 371 °C.
Average melting point of Li and K = (454 °C + 330 °C)/2 = 784 °C/2
= 392 °C
Eat eat eat eat eat eat eat eat eat
Answer:
The electron cloud
Explanation:
<em>Rutherford’s gold foil experiment</em> showed that the atom consisted of a tiny nucleus inside of a much larger electron cloud.
The diameter of the electron cloud is about 50 000 times that of the nucleus.
The correct answer is letter B. Genetic engineering has shown a great leap in Science because we can now harness the ability of mutations of cells in crops and in other aspects. Flour is a commodity that is greatly needed by the masses and learning how to genetically modify its components to help it breed better is a great advantage for any society.
