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
Answer:
Explanation:
Both motion of particles and temperature increase
Answer:
Gravity is very important for us,animals and plants. We could not survive Earth without it. The sun's gravity keeps Earth in orbit around it, keeping us a good distance away from it (the sun). Gravity is holding down our atmosphere and the air we need to breathe along with it.
Answer: F. Electron pair acceptor
Explanation:
A Lewis acid can be properly defined as any substance such as H+ (hygrogen ion) that can accept a pair of electron.
While a Lewis base is any substance such as (OH-) that can donate a pair of electron.
In the neutralization reaction between an acid ( H+ ) and a base (OH-). Hydrogen ion (H+ ) is the Lewis acid because it accepts an electron pair from (OH-).
Other examples of Lewis acid are; Mg2+, K+
