Answer:
We can tell by how the continents look. Scientists who propose the pangea theory have said this. You can see for yourself because all the continents look like puzzle pieces you could put together. Scientists can also tell from the species. For example, let's say a scientist found a bone of a creature at the edge of a continent, the edge of another would have the same species. They have also calculated that the continents in itself are still splitting apart, but very slowly. The reason they split up was because tectonic plate movements.
The elements in Groups 1A(1) and 7A(17) are all quite reactive.
<h3>Major difference between Groups 1A(1) and 7A(17) : </h3>
Group 7's halogens, which are non-metal elements, become less reactive as you move down the group. In contrast to the alkali metals in Group 1 of the periodic table, this trend is the opposite. The most reactive element in Group 7 is fluorine.
Alkali metals are soft and reactive metals. They react vigorously with water and become more reactive. And other hand halogens are reactive non metals.
- Elements of group 1A are known as alkali metals. Elements of this group are lithium, sodium, potassium, rubidium, cesium.
- Reactivity increase down group 1 but decrease up group 7 this is because group 7 elements react by gaining an electron. As one move down the group, the amount of electron shielding increases, meaning that the electron is less attracted to the nucleus.
To know more about Groups 1A(1) and 7A(17) please click here :
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