Or use the REST API:
http://rest.ensembl.org/lookup/id/ENSG00000228321?content-type=application/json will give you:
{"source":"ensembl_havana","object_type":"Gene","logic_name":"ensembl_havana_gene","species":"homo_sapiens","description":"tumor necrosis factor [Source:HGNC Symbol;Acc:HGNC:11892]","display_name":"TNF","biotype":"protein_coding","end":31617784,"seq_region_name":"CHR_HSCHR6_MHC_MANN_CTG1","db_type":"core","strand":1,"id":"ENSG00000228321","start":31615015}
and
http://rest.ensembl.org/lookup/id/ENSG00000232810?content-type=application/json will give you:
{"source":"ensembl_havana","object_type":"Gene","logic_name":"ensembl_havana_gene","species":"homo_sapiens","description":"tumor necrosis factor [Source:HGNC Symbol;Acc:HGNC:11892]","display_name":"TNF","biotype":"protein_coding","end":31578336,"seq_region_name":"6","db_type":"core","strand":1,"id":"ENSG00000232810","start":31575567}
As you can see the "seq_region_name" gives you name of the chromosome on which the gene in question is located.