Correct Way to Grouping Group Checkboxes in HTML5

Can you please let me know which way is the correct way of grouping the Name attribute of a series of related checkboxes in together in HTML5? I have seen some tutorials on the web which are only using simple name as name="chk_group" like below

<input type="checkbox" name="chk_group" value="value1" />Value 1<br />
<input type="checkbox" name="chk_group" value="value2" />Value 2<br />
<input type="checkbox" name="chk_group" value="value3" />Value 3<br />

how ever some people are using an array like name="chk_group[]"

<input type="checkbox" name="chk_group[]" value="value1" />Value 1<br />
<input type="checkbox" name="chk_group[]" value="value2" />Value 2<br />
<input type="checkbox" name="chk_group[]" value="value3" />Value 3<br />

can you please let me know what is the correct way in HTML5?

Thanks