Why is XML element invalid?

Question

<?xml version="1.0" ?>
<accounts>
    <1167/>
    <1328/>
    <1505/>
    <1536 default="true" />
    <1966/>
</accounts>

When I pass in the above XML at http://www.w3schools.com/XML/xml_validator.asp I get an error stating the line with <1167/> is invalid. I looked at the w3 description for elements, and didn't see any reason why it should be wrong. I'm sure its a simple mistake so would appreciate any help.

Thanks

Answer 1

The name of an element must not start with a digit¹.

Also, the name of an element should describe the "class" or "type" of the represented entity, and be static. Might I suggest:

<accounts>
    <account number="1167"/>
    <account number="1328"/>
    <account number="1505"/>
    <account number="1536" default="true" />
    <account number="1966"/>
</accounts>

¹ _{For some reason, many answers here link to w3schools (which is not affiliated with the W3C). Instead, you should only trust the XML standard.}